|This article has multiple issues. Please help improve it or discuss these issues on the talk page.|
The following is a list of characters from the American situation comedy The Big Bang Theory created and executive produced by Chuck Lorre and Bill Prady, which premiered on CBS on September 24, 2007. It concerns two prodigies in their 20s, one a theoretical physicist and the other an experimental physicist, who work at Caltech and live across the hall from a waitress with show-biz aspirations. Their geekiness and intellect are contrasted by her social skills and common sense.
These characters have been with the series since its inception. With the exception of injury to the actors, these characters have appeared in all episodes.
- Dr. Leonard Leakey Hofstadter (Johnny Galecki) is an experimental physicist with an IQ of 173 originally from New Jersey who received his Ph.D. when he was 24 years old. He shares an apartment in Pasadena with colleague and friend Sheldon Cooper. The writers have toyed with a romance between him and next-door neighbor Penny since the pilot, with their unresolved sexual tension being a major force for drama. Leonard dated Penny for most of Season 3, although they had dated briefly at the end of Season 1. Aside from Penny, Leonard has had romantic relationships with co-worker Dr. Leslie Winkle, physician Dr. Stephanie Barnett, an unnamed French literature PhD, and North Korean spy Joyce Kim. Following his breakup with Penny, Leonard began a relationship with Raj's sister Priya, and it is implied they had a brief sexual encounter before the start of the series on an occasion when Priya visited Raj. The two attempted a long-distance relationship when Priya moved back to India, but Leonard eventually dated a girl he met at the comic book store while Priya admitted to sleeping with her old boyfriend. In Season 5's "The Beta Test Initiation", Leonard and Penny start dating anew. Leonard's family includes two other accomplished scientists: his mother, Dr. Beverly Hofstadter, and his sister, a biologist, while his brother Michael is a Harvard law professor, and his father an anthropologist.
- Dr. Sheldon Lee Cooper (Jim Parsons) is a theoretical physicist, possessing a Bachelor of Science, Master of Science, Master of Arts, a PhD, an ScD, and an IQ of 187. Originally from East Texas, he was a child prodigy, starting college at the age of 11, and receiving his PhD at age 16. He is calculating, and refrains from any form of physical contact if possible. Sheldon exhibits a strict adherence to routine to the point of exhibiting obsessive–compulsive disorder, including a complex "Roommate Agreement" with Leonard. He has shown a lack of understanding of irony and sarcasm and presumes an emotionally detached superiority to others. Sheldon loves comic books and is a fan of Spock, a fictional character of Star Trek franchise. Unlike the situation with Leonard's family, Sheldon is unique among his family members: his father, George, whose death pre-dates the series, was described as a stereotypical Texan who liked football, skeet shooting, and heavy drinking; his mother, Mary, is a devout Evangelical Christian, who does not possess anything near Sheldon's intellect (though she displays a great deal of common sense); his twin sister, Missy, and as-yet unseen brother, George Jr., were both described by Mary as being "dumb as soup". Whenever he tells a joke, or plays a prank, he typically punctuates it with the word "Bazinga!". Sheldon tends to bully his friends into complying to his whimsical demands. He is presumptuous and makes highly inappropriate comments at the wrong times. A common joke is his inability to drive, although he did receive a learner's permit
- Penny (family name currently unrevealed) (Kaley Cuoco), is Leonard and Sheldon's neighbor across the hallway. Originally from a small town outside of Omaha, Nebraska, she is a waitress at the local Cheesecake Factory and also an aspiring actress. She has dated several men during the course of the series, including Kurt, Stuart and Zack. Leonard pursued Penny during season 1; they dated briefly at the start of season 2 which led to some awkwardness; they began dating again and were a couple for most of season 3 but she broke up with him after he told Penny he loved her and she was not ready to reciprocate; however, she has regretted this decision at times. She has been influenced somewhat by the guys, including an obsession with on-line gaming, making references to Star Trek, and realizing that she could no longer date unintelligent men. She is often irritated by Sheldon's nerdy, socially detached personality, but at times, they have shown to be good friends. Penny and Leonard begin to date again "slowly" during the fifth season, though he does upset her by accidentally asking her to marry him during sex. Their relationship continues into the sixth season, although there is strain from the proposal. By season four, Bernadette, Amy and Penny have formed their own group as a subset of the entire cast that likes to hang out in Penny's apartment, go out together and comfort each other.
- Howard Joel Wolowitz (Simon Helberg) is an aerospace engineer at Caltech's Department of Applied Physics who often hangs out at Leonard and Sheldon's apartment. Unlike Sheldon, Leonard, and Raj, Howard lacks a doctorate, and often is downgraded as a result, especially from Sheldon. He defends this by pointing out that he has a master's degree in Engineering from MIT and that the equipment he designs is launched into space, unlike the theoretical work of his friends. In the season 5 finale, Howard goes to the International Space Station on Expedition 31. Howard lives with his overbearing and unseen mother in Altadena, who treats him like a child. While he sometimes expresses irritation at this treatment, for the most part he appears to prefer it. Howard, in turn, dotes on his mother and participates in many of her daily routines. His father left them when he was 11, and, to date, he has never learned why. Howard fancies himself a ladies' man and attempts pick-up lines whenever a female is present, which often comes off as inappropriate and disgusting, although he appears to have dropped this habit. He is Jewish, although he is not very serious about his faith, and does not keep kosher. In the pilot episode, it's shown that he is a polyglot and can speak English, French, Mandarin, Russian, Arabic, and Farsi, along with fictional languages like Klingon and Elvish. He is asthmatic, allergic to peanuts, almonds and walnuts, prone to canker sores and pink eye, succumbs to seasickness, has an incredibly high genetic risk of heart illness, and has transient idiopathic arrhythmia. In Season 5 episode 4, it's shown that he knows ASL (American Sign Language) which is helpful when Penny introduces Raj to a deaf friend of hers, whom Raj begins to date. Howard dated Bernadette Rostenkowski briefly in season 3. After some difficulties, they resumed their relationship in season 4, which culminated in their engagement. In season 5, Howard and Bernadette are married on the roof of the apartment building the day before he has to go into space.
- Dr. Rajesh Ramayan"Raj" Koothrappali (Kunal Nayyar) is Howard Wolowitz's best friend, and yet another genius of the group; his name is usually shortened to "Raj". He is originally from New Delhi, India, and he works in the Physics department at Caltech, where his area of expertise is particle astrophysics. He lives in an apartment in Pasadena. As with his friends, he is mutually involved with and obsessed with science fiction and comic books in general, and is usually the one to propose various real-life questions derived from such works, such as the functions of the tails of the Na'vi in the film Avatar. Raj hates India, Indian food and Indian music, however, he does appreciate the Indian lullabies his mother sang to him and the catchiness of Hindi phrases. Raj is a Hindu and believes in karma (reincarnation), but eats beef. Raj is extremely shy around women, and finds himself unable to speak to or while in the presence of them unless he drinks alcohol (but in one case, he took experiment drugs which allowed him to speak with women, and once had a placebo effect when he drank non-alcoholic beer unaware of it). When Penny or Bernadette is around, Raj usually whispers what he wants to say to Howard or Leonard, who then repeats or responds to what Raj says out loud. Despite this, Raj has often ended up in bed with women, leaving the other guys perplexed. Raj comes from a very wealthy family in India, and often communicates with his parents, Dr. and Mrs. Koothrappali, via webcam.
These characters started out as recurring characters, and were later promoted to main cast. These characters do not appear in all episodes, and are only credited in episodes in which they appear.
- Dr. Leslie Winkle (Sara Gilbert) (appeared in eight episodes total, four credited as main cast) is an optical physicist who works in the same lab as Leonard. In appearance, she is essentially Leonard's female counterpart, equipped with the black framed glasses and sweat jackets. She is Sheldon's arch-enemy, due to their conflicting scientific theories. Though they both consider each other to be intellectually inferior, Leslie is much wittier than Sheldon, regularly calling him "dumbass" and besting him in their repartée. Leslie has had casual sex relationships with Leonard and later Howard. Leslie stopped appearing in the series after the finale of season 3, when Leonard, being desperate for physical contact, asked to get back on with Leslie. She closed the door in his face and did not appear.
- (Dr. after "The Roommate Transmogrification") Bernadette Maryann Rostenkowski (Rostenkowski-Wolowitz after marriage to Howard) (Melissa Rauch): (appeared in 30 episodes total, 25 credited as main cast) is a waitress and co-worker of Penny at the Cheesecake Factory, which pays the way for her graduate studies in microbiology per "The Creepy Candy Coating Corollary". A recurring joke on the series is reference to Bernadette handling infectious biological specimens before preparing food or making physical contact with people, which eventually results in her and her entire research team spending New Year's Eve 2010 in quarantine. She is of Catholic upbringing, having gone to a Catholic school - she admits that she cannot lie very well because, according to her, the teachers "kind of whip that out of you" - and is frequently seen wearing a cross necklace. Bernadette is introduced to Howard by Penny after he invoked the Girlfriend Pact. At first, she and Howard do not get along, as they appear to have nothing in common. When they find out that they both have overbearing mothers, they feel a connection. Subsequently, Howard realizes Bernadette presents a real opportunity to develop a lasting relationship, and, in an impulsive manner, he proposes to her. Although Bernadette rejects his offer, they remain a couple for a time after Howard sings a heartfelt song for her at the Cheesecake Factory, which Penny finds quite embarrassing, but Bernadette finds romantic. Eventually, they break up after she discovers Howard, via his World of Warcraft character, having sex with another online character. Bernadette and Howard reconcile and resume their relationship, ultimately culminating in their engagement in the season 4 episode, "The Herb Garden Germination". In "The Roommate Transmogrification", she finally obtains her Doctorate and is subsequently hired by a pharmaceutical company that promises her "a buttload of money". This makes Howard jealous, especially after the rest of his friends taunt him about his lack of a Doctorate. It eventually leads to them having an argument after she purchases a Rolex watch for Howard, which he interprets as her "rubbing in" the fact that she now earns more than him. Howard later learns that Raj fantasizes about Bernadette and writes love poems about her.  Bernadette almost broke up with Howard after hearing about his previously unknown former sexual escapades that came out during his bachelor party from the episode "The Stag Convergence". Howard and Bernadette are married (by the entire gang) on the roof of the apartment that day before he has to go into space.
- Dr. Amy Farrah Fowler (Mayim Bialik, Ph.D.) (appeared in 26 episodes total, 21 credited as main cast) is a neuroscientist (which corresponds to Bialik's real-life Ph.D.). Raj and Howard met Amy through an online dating site after secretly setting up an account using Sheldon's name and information. The site matches her to Sheldon, and the two share many similar traits. Once she and Sheldon meet, she becomes, as Sheldon puts it, a girl who is his friend, but not his "girlfriend". To emphasize the difference, Sheldon and Amy refer to each other as "boy-slash-friend" and "girl-slash-friend". They briefly ended their friendship when they got into an argument over whose field of study was superior. The two initially communicate only by text message and occasionally via webcam, though she gradually began hanging out with the gang in person through the fourth season. After they announce their intention to have a child, Penny suggests and then ends up chaperoning their first date together since Sheldon doesn't drive. In Season Five, Amy made Sheldon jealous by going on a date with comic book store owner Stuart, causing Sheldon to solidify their relationship as boyfriend/girlfriend with a 31-page "Relationship Agreement". Amy began a campaign in "The Launch Acceleration" to increase Sheldon's feelings for her by treating him nicely and becoming more involved in his interests like video games and Star Trek. During Howard and Bernadette's wedding ceremony, Amy is disappointed when Sheldon says that he hopes that the two of them are as happy together as he is alone. Later as Howard is launched into space, Amy is surprised when Sheldon does take her hand. Besides being friends with Sheldon, Amy also injects herself into Penny's life and attempts to bond with Penny and Bernadette (even considering Penny to be her best friend, or "bestie") becoming part of "Penny's posse" as they hang out in her apartment, go out together and supporting each other emotionally. Amy frequently makes them uncomfortable by misinterpreting "girl talk" to mean openly discussing topics such as female anatomy and feminine hygiene and being somewhat condescending to Bernadette. While Amy has indicated a desire to experience physical intimacy with Sheldon (a sentiment Sheldon doesn't share), she also often displays a bisexual side, including making inappropriate comments about Penny's body, indicating a physical attraction to her. In episode 8 of the fifth season, she shows a disturbing enthusiasm on the whim that Bernadette's bridal shower should consist of naked bridesmaids washing each other, and she proposes that the bachelorette party consist of a Native American sweat lodge and women dancing around painting fertility symbols on the bride's naked body. When Penny offers to cut Sheldon's hair after his regular barber is hospitalized in "The Werewolf Transformation", Amy told them that there wasn't a hair on her body that she would not let Penny cut. Amy, although first viewed by the others as inhibited and aloof, soon becomes enthusiastic and craves a social life. She enjoys Penny's company and occasionally notes that her entire social life depends on Penny. In "The Shiny Trinket Maneuver", Amy has a very girly side, and falls in love with a tiara (an apology present from Sheldon). She's shown to have something of an arrogant side in "The Pulled Groin Extrapolation", where she's convinced that Leonard has fallen for her after he accompanies her to a friend's wedding and gives her a chaste kiss on the cheek, even though he has no such feelings. In "The Isolation Permutation", Amy reveals that she had very few friends from pre-school through grad-school. Amy Farrah Fowler has a Ph.D. in neurobiology, with a research focus on addiction in primates and invertebrates. She has successfully taught a monkey to smoke cigarettes, and has nearly got a starfish hooked on cocaine. In "The Benefactor Factor", it is revealed that she is technically engaged to Saudi Arabian Prince Faisal who resides in Riyadh, who is the source of much of her lab's funding. Amy can also play the harp. The actress portraying Amy Farrah Fowler, Mayim Bialik, was mentioned by Raj ("the girl who played TV's Blossom") in episode 1.13, "The Bat Jar Conjecture", as a possible substitute for Sheldon on their Physics Bowl team.
These characters appear in several episodes. The list is sorted by chronological order of appearance, considering their first appearance in the show.
- Dr. Eric Gablehauser (Mark Harelik): The head of the Physics Department, Dr. Gablehauser is the group's boss at the university. In his first appearance, he fired Sheldon after Sheldon insulted his intelligence. Eventually, Sheldon was rehired because Gablehauser became romantically interested in Mary Cooper, Sheldon's mother. Gablehauser refers to Sheldon, Leonard and Rajesh as doctors, but to Howard as "mister" because he lacks a Ph.D (but carries a Masters Degree). Dr. Gablehauser was also responsible for introducing child genius Dennis Kim to the university and for hosting the Physics Bowl.
- Mary Cooper (Laurie Metcalf): A devout Fundamentalist Christian from Texas, Mary is Sheldon's mother. She has two other children besides Sheldon; Sheldon's twin sister, Missy and his brother George, who is shown via a family tree in "The Cruciferous Vegetable Amplification" to be three years older than Sheldon and Missy. She appeared in the fourth episode of the first season, the season three premiere, the third episode of season four, and the sixth episode of season five. Mary herself is not intellectual but is very wise, and prone to making politically incorrect comments; such as referring to "kung fu letters" when Leonard takes her to a sushi restaurant, or saying that "I thought it was our Indians that had the occasional drinking problem" when she sees Raj drunk. She appears to be an extremely good mother and is the only one who has ever been able to control Sheldon. Leonard described Mary as Sheldon's "Kryptonite". When Penny and Sheldon engaged in a fierce dispute, Penny called for Mary's help, who subsequently called and scolded Sheldon about his actions. Leonard wishes his mother was as loving as Sheldon's mother, although Sheldon himself appears at best ambivalent about her parenting. It is once mentioned by Sheldon that Mary once hit him with a bible because he refused to eat his brussel sprouts.
- Mrs. Wolowitz (voiced by Carol Ann Susi): Howard's overbearing Jewish mother, she is never seen on-screen but her deep voice is heard when he is at their house or when he talks to her on the phone. She talks to Howard always by yelling at him from another room, which results in awkward conversations with Howard yelling back at her. In an early episode, when the guys heard her yelling in a masculine voice, they asked Howard if that was his father; to which he replied "If she grows any more hair on her face, yes"; hinting that she suffers from facial hair growth. Mrs. Wolowitz seems to be oblivious about Howard's work as an engineer, and talks to him like he is still a child. She frequently refers to Leonard, Sheldon and Raj as Howard's "little friends" when yelling to him (as in, "I made some cookies and Hawaiian Punch for you and your little friends!") She makes Howard's life miserable at home, which prompts him to call her a "crazy old lady". However, in one episode, Howard attempted to move out, but had serious delusions that his mother was trying to force him to stay, when in actuality, she was urging him to move out, so he stayed. In the season 4 finale, she wants to "play doctor" with Raj when he asks to sleep over. When Howard revealed that he proposed to Bernadette and she accepted, she collapsed, causing Howard to panic (and dislocate his shoulder trying to barge into the bathroom to help her), and the timing leads him to believe that she may not have liked Bernadette and had suffered a heart attack from the shock of the news. In actuality, her fainting was, coincidentally, due to food poisoning from the food she ate while meeting Bernadette, and was completely unrelated to Howard's news. She has accepted Bernadette as her future daughter-in-law and loves that she is a doctor. She attended Howard and Bernadette's wedding on Leonard/Sheldon/Penny's apartment building roof and can be seen in the satellite picture of the event.
- Dr. V.M. Koothrappali (Brian George) and Mrs. Koothrappali (Alice Amter): Raj's parents in India, they communicate with their son via video chat and constantly try to arrange dates for him. They want their son to marry a woman of Indian descent, and give them grandchildren. Mrs. Koothrappali is especially worried that, despite Raj being old enough to marry, the closest they have to a daughter-in-law is the "Jewish boy", Howard. Although in many episodes Raj mentions that he grew up in poverty, his friends remind him of the contrary by pointing out that Dr. Koothrappali is a gynaecologist and drives a Bentley. To this, Raj replies "It's a lease". The Koothrappalis enjoy Doogie Howser reruns, which are apparently new to India. Other than Raj, they also maintain contact with Priya Koothrappali via video chat whenever she is out of India. They also had some anger towards Leonard when it became apparent that he was dating Priya without their knowledge.
- Dr. Stephanie Barnett (Sara Rue): A doctor and highly distinguished surgical resident at Fremont Memorial, Stephanie is first seen as Howard's date, but later becomes Leonard's girlfriend. When Howard's plan to let her drive the Mars rover failed, she left with Leonard and the two immediately became attracted to each other. Sheldon began meddling in Stephanie and Leonard's new relationship in an effort to consolidate it, since in his eyes, Stephanie was the only "tolerable" mate Leonard had had. After several weeks of dating, Stephanie officially began living with Leonard in his and Sheldon's apartment. However, after much hesitance, Leonard told her to move out because he was uncomfortable with the pace of the relationship. Although they were not seen breaking up on camera, evidence suggests their relationship ended. Series co-creator Bill Prady confirmed this in an interview, stating: "Stephanie was a chance for Leonard to learn that just because someone loves you, doesn't mean you'll love them back". Stephanie did her medical internship at Lawrence Memorial in Galveston, Texas, which is where Sheldon was born.
- Dr. Beverly Hofstadter (Christine Baranski): Leonard's overly analytical mother, Beverly is a neuroscientist as well as a psychiatrist. Between her neurotically strict speech patterns, lack of social conventions, and attention to detail, she is Sheldon's female equivalent. The two of them share an odd non-romantic attraction to each other, which culminates in her kissing him after becoming drunk. Though still married to Leonard's father, she revealed in an appearance that the two "are getting a divorce". She had frequently implied that the two have not had "coitus" since Leonard was conceived. She diagnosed Raj with selective mutism and considered Raj and Howard's relationship to be an "ersatz homosexual marriage". Beverly mentioned that Leonard's brother and sister are more successful in their respective fields than he is. Ironically, as displayed in "The Maternal Congruence" episode, Sheldon is closer to Beverly than her own son is. In both 2009 and 2010, Christine Baranski was nominated for an Emmy Award for Outstanding Guest Actress in a Comedy Series for this role. She returns via Skype for the season 5 premiere.
- Barry Kripke (John Ross Bowie): An unlikable co-worker of Leonard and Sheldon's, who works in plasma physics, Kripke has a case of rhotacism where he pronounces the letters "R" and "L" as "W" in much the same way as Elmer Fudd from Looney Tunes. In his first appearance, he pitted his robot, the Kripke Krippler (or, as he called it, the "Kwipke Kwippwuh"), against the guys' robot, M.O.N.T.E., in an unofficial robot fight. On another episode, Sheldon attempted to befriend Kripke in order to gain access to an open science grid computer to carry out research, but it turned out to be futile, as Kripke had no control of the computer as Sheldon had thought. Kripke continued his antagonism towards Sheldon, when he pulled a prank on Sheldon when the latter was a guest on NPR's Science Friday. Sheldon tried to befriend Kripke another time when he was feeling left out from his friends, but Barry connected more with the others in Sheldon's new proposed group. Kripke purchases an iPhone with voice recognition technology, but due to his rhotacism, the device is incapable of understanding his verbal "wequests". In Season 5's "The Rothman Disintegration", Kripke and Sheldon battle over a retiring professor's office. At Howard's Bachelor Party during the "The Stag Convergence" episode, Kripke uses his toasting turn to complain that there were no strippers at the party; his presence at the event does indicate that he and the main group of friends do at least tolerate each other (or that Howard, like Sheldon and Leonard and Raj, has so few friends that Kripke hangs around them by default).
- Stuart Bloom (Kevin Sussman): Stuart runs the comic book store that the guys frequently go to. He is also a nerd, but he has a talent for drawing, is a graduate of Rhode Island School of Design and possesses a few more social skills than they do. During Stuart's first appearance, the guys brought Penny along to the store and he managed to ask her on a date. The date went fine until Stuart was dragged into discussing comic books by Sheldon, leaving Penny bored. On a second date with Penny, Stuart asked for Leonard's advice, but feeling threatened, Leonard ultimately gave him bad advice. The date went fine, but when Penny was getting romantic with Stuart she mistakenly called him "Leonard", leaving him devastated. Stuart was the partner of Wil Wheaton in the card game tournament, where they defeated the pair formed by Raj and Sheldon. As Stuart runs a comic book store, he has an almost encyclopedic knowledge of comic books and superheroes. In the Season 4 episode "The Toast Derivation", he implied he was in financial trouble and that the comic book store is now also his home. In "The Justice League Recombination", he stated that he works 70 hours and clears an average of $1.65 per hour after expenses, so his income per week would be $115. At Howard's Bachelor Party during the "The Stag Convergence" episode, Stuart uses his toasting turn to tell Howard lucky he was and how lonely he was living in the back of a comic book store.
- Wil Wheaton (portraying an antagonistic version of himself): In the season 3 episode "The Creepy Candy Coating Corollary", Sheldon enters a card game tournament (Mystic Warlords of Ka'ah) to confront Wil Wheaton over an incident that occurred in 1995 when Sheldon was devastated because Wheaton (Wesley Crusher in Star Trek: The Next Generation) failed to show up at a fan convention that Sheldon took a 10-hour bus ride to attend (in which he had to "twice violate his personal rule of no relief on a moving vehicle"). In the final match, Sheldon is about to defeat his hated rival, but Wheaton tells Sheldon that the reason he missed the convention was because his grandma had died. After Sheldon wastes his last opportunity to win under sympathy, Wheaton reveals that he lied about his grandma allowing him to win the game. Wil Wheaton makes a second appearance in the episode "The Wheaton Recurrence", where he uses gamesmanship again as seen when he breaks up Leonard and Penny's relationship in order to win a bowling competition against the main characters. In "The 21-Second Excitation", Wheaton appears at a screening of Raiders of the Lost Ark, in which he uses his celebrity status to go to the front of a long line. This antagonizes Sheldon, who derides him as the "Jar Jar Binks of the Star Trek universe". Wheaton and his entourage effectively prevent Sheldon and the guys from attending the screening when the last seat in the theater goes to the person directly in front of them in line. Ultimately, Sheldon steals the prints of the film and Wheaton leads a mob of angry Raiders fans after Sheldon, Howard, Raj and Leonard. In the Season 5 episode "The Russian Rocket Reaction", Wheaton appears to be genuinely sorry for his past actions, and gives Sheldon a signed Wesley Crusher action figure as a way of thanking Sheldon for being a fan. His gesture is met with a renunciation of his "mortal enemy" status, and a hug from Sheldon. Along with LeVar Burton, Leonard Nimoy, Brent Spiner and George Takei, Wheaton makes Star Trek the most represented franchise on the show in terms of guest appearances. At Howard's Bachelor Party during the "The Stag Convergence" episode, Wil video-records the toasts and uploads them to the internet, getting Howard and Raj in trouble with Bernadette and showing that he hasn't lost all of his "evil" quirks.
- Zack Johnson (Brian Thomas Smith): A dim-witted beefcake-type who Penny dates after her second break-up with Leonard. Leonard invites Penny and him up on the roof to watch his experiment of bouncing laser beams off the moon; Zack has no clue what is happening. Later, he and Penny go out on a date, but she is so put off at how stupid he is that she runs back to Leonard to have sex, saying that Leonard has ruined her ability to date stupid men. In a later episode, he runs into Penny, Bernadette, and Amy at a restaurant, and Amy becomes physically attracted to him. Unlike Penny's other boyfriends, he considers Leonard, Howard, Sheldon, and Raj (whom he calls "the science guys") to be "cool" and makes a genuine effort to get to know them, considering them his friends. After accompanying them on a trip to the comic book store (he and Raj bond over a mutual fondness for Archie comics), he enters a New Year's Eve costume party with them, portraying Superman in their version of the Justice League. He works as the menu designer for restaurants either owned or who employ his father's company to design their menus. In "The Toast Derivation", Sheldon invites him over for a party, where he bonds with Barry Kripke and Stuart as well.
- Priya Koothrappali (Aarti Mann): Raj's sister, a lawyer who graduated at the top of her class at Cambridge. Introduced in the fourth season, it is implied upon her first appearance in "The Irish Pub Formulation" episode that she and Leonard had a relationship five years earlier (without her parents' or Raj's approval) when she was in town, and that Leonard had been much more invested in the relationship than she. Leonard even offered to relocate to Delhi to be with her. He tries to keep their relationship a secret from the guys, but Sheldon discovers Priya in their apartment. Leonard eventually reveals to the rest of the guys that he had spent the night with Priya, as he is unable to bear the burden of keeping the secret. Priya returns to Los Angeles for business in "The Cohabitation Formulation", and she and Leonard decide to try and have a real relationship, over the protests of Raj. It upset Raj to know that his sister was having sex with or even taking off her clothes in front of one of his best friends (sometimes in Raj's bed). Priya soon becomes jealous of Penny, and asks Leonard to stop spending time with her. Priya contests Sheldon's roommate agreement with Leonard, employing her legal background to deny Sheldon power over Leonard, but Sheldon drafts a new agreement and blackmails Leonard into signing it. Sheldon then threatens to tell Priya's parents she is dating Leonard, which she cannot bear because they want her to either date an Indian or, possibly, a "nice Jewish boy like Howard." In the fourth season finale, it is revealed she is moving back to India and has not told Leonard, which Leonard interprets as the end of their relationship and causes him to expose their secret relationship to her parents. Although they are then separated with Priya moving back a month earlier than expected, they nonetheless remain in-touch via webcam, having a cyber-dinner date/breakfast date. At Howard's suggestion, Leonard and Priya also attempted to simulate sex via webcam, but when it came time for her to remove her clothing, Leonard's screen froze up because of exceeding the bandwidth. Leonard later managed to get cue cards to help himself with a seduction speech to Priya, but while delivering it to her, he inadvertently revealed to her parents that they were cyber-dating (they were in the same room as her when he called), with them bitterly asking for him to continue with the speech. After Leonard tells Priya about his attraction to a comic book enthusiast named Alice, Priya admits to recently sleeping with her ex-boyfriend, which visibly upsets Leonard. She claims that its not a competition, to which he replies that it is and that she won. Then he switches off his labtop. In the next episode, Leonard refers to himself as "single", indicating he and Priya have broken up as a result of their last conversation.
These characters appear in fewer episodes, most in just one. The list is sorted by chronological order of appearance, considering their first appearance in the show.
- Althea (Vernee Watson) A character that made an appearance in the pilot episode as an attendant at a sperm bank, and then made three appearances as an emergency room nurse in "The Peanut Reaction" episode (Season 1) and "The Robotic Manipulation" episode (Season 4), and a ward nurse in "The Werewolf Transformation" (Season 5). The name of the character is never used on the show, only on her nametag and in the credits.
- Kurt (Brian Patrick Wade): A tall, intimidating body-builder, Kurt is Penny's ex-boyfriend at the beginning of the series. In the pilot-episode, Leonard and Sheldon went to his apartment and tried to retrieve Penny's TV set from him, but they did not succeed and returned home without pants. Penny left him because he cheated on her, but he was still invited to her Halloween party, for which he dresses up as a caveman. In season 2, ep14, Penny experiences financial difficulties, Leonard and the guys confront Kurt over $1800 in legal fine money Penny had lent him; immediately refusing, Kurt shortly thereafter pays Penny and the two have dinner.
- Chen (James Hong): The owner of a Chinese restaurant the guys frequently visit.
- Christy (Brooke D'Orsay): An acquaintance of Penny from Nebraska who had slept with enough of her relatives to make her "family", Christy suddenly moves in with Penny when she comes to California. Being promiscuous, Christy ends up sleeping with Howard forcing Penny to sleep on Leonard's couch, who in turn invites her to move in with him (and his mother). Mrs. Wolowitz and Christy end up having a fight, and the latter leaves.
- Lalita Gupta (Sarayu Rao): A childhood acquaintance of Raj, she is now a dental student at USC. Raj's parents set up a date for their son with her. During the date, Raj can only speak to her after drinking an alcoholic beverage (a "grasshopper"). Sheldon insists she bears a remarkable resemblance to Princess Panchali, an Indian princess in a children's story. Lalita is flattered at Sheldon's comments and attention. Eventually, Lalita leaves the obnoxious and drunk Raj to have dinner with Sheldon. Sheldon does not see her again because he "already has a dentist".
- Toby Loobenfeld (DJ Qualls): A research assistant with a double major in Physics and Theater, Toby was used by Sheldon to play his fictional first cousin "Leopold Houston" from Denton, Texas, a character Sheldon invents as part of an elaborate lie told to avoid going to see Penny sing. Cousin "Leo" is a recovering drug addict who ends up cuddling with Penny on the couch, much to the chagrin of Leonard. He was also willing to argue with Sheldon on the subjects regarding drug use, showing knowledge on the subject.
- Dennis Kim (Austin Lee): Dennis is a 15 year old child prodigy from North Korea whom Dr. Gablehauser hopes to recruit into their Ph.D. program. Dennis and Sheldon have an antagonistic relationship when the former excels Sheldon in every way. The guys make arrangements so Dennis can meet girls of his age and get distracted from his own research. The plan succeeds and Dennis is seen kissing with a girl and becoming being homeless in the park, no longer an intellectual threat to Sheldon.
- Missy Cooper (Courtney Henggeler): Missy is Sheldon's twin sister who is intellectually and socially very much unlike him. Confident, tall and attractive, she immediately catches the attention of Leonard, Howard, and Raj. Sheldon realizes that within Missy's eggs lies the potential for another "superior mutation" like him. He temporarily erects himself as a guardian to Missy in order to choose the best mate for her (she rejects Leonard and Howard in favour of Raj, but his mutism derails any chance he might have with her). Missy objects to Sheldon deciding who she can sleep with, refers to Sheldon as "Shelly", and despite their differences she loves him and is proud of his accomplishments.
- Blain (Tyler Olson) and Tom (Mark Hames): A couple of guys Sheldon tries to fix up with Penny in order to help break her video game addiction. In his clumsiness, Sheldon gives Blain the incorrect impression that he is inviting him on a date (with sex) rather than fixing him up on a date with a woman (Penny). Tom is a person whom Sheldon finds in an online dating service who was matched to Penny because he likes the woman to be the sexual seducer.
- Ramona Nowitzki (Riki Lindhome) and Kathy O'Brian (Emily Happe): A couple of female graduate students, who both have a crush on Sheldon, and become his 'groupies.' Sheldon exploits them to get free food and perform personal services. Ramona is the first, first meeting Sheldon after he introduced his work to incoming graduate students. She finds Sheldon's work very stimulating and him very cute to the utter confusion of his friends and arranges to have dinner with him in his apartment. The next few days she becomes a permanent presence in his life, pressuring him to concentrate on his research and avoid distractions such as video games, sci-fi television shows and weekend paintball expeditions. Sheldon gets tired of her but is unable to dissolve their "relationship". Eventually, Sheldon reaches a breakthrough in his work, and kicks Ramona out when she asks to share credit for the discovery. Kathy comes into Sheldon's life after he kicked Ramona out.
- Dr. David Underhill (Michael Trucco): A MacArthur Genius Grant recipient, David is an experimental physicist like Leonard, who is excited to be working with him. With his leather jacket and handsome looks, Penny is shocked to know that David is a scientist and starts dating him. They break up when she finds out he is married.
- Alicia (Valerie Azlynn): A young blonde who moves into an apartment above Leonard and Sheldon in the Dead Hooker Juxtaposition. Penny displays a fit of jealousy at this turn of events, thinking that Alicia is supplanting her in the boys' attention. Alicia is an actress, although more successful than Penny, having landed a role on CSI as a (dead) prostitute. Eventually, to Howard's delight, she and Penny get into a catfight over her treatment of the guys. After the catfight, Penny says Alicia is a "dead whore on TV; live one in real life" just before the gang hears Alicia having sex with a CSI producer.
- Dr. Crawley (Lewis Black): An entomologist at the University, Dr. Crawley is visited by Sheldon, Howard, and Raj in order to identify the species of a cricket they found. He is agitated at losing his position at the university, his lab, and, as a result of an extended research trip, his wife.
- Bethany (Molly Morgan), Sarah (Sarah Buehler), and Skeeter (Andy Mackenzie): Characters who appear in "The Gothowitz Deviation" episode. Bethany and Sarah are a couple of girls that Wolowitz and Raj meet in a Goth club. They then go to a tattoo parlor, where Skeeter is the tattoo artist. The name "Skeeter" is not used on the show, but appears in the credits.
- "Captain Sweatpants" (Ian Scott Rudolph) and "Lonely Larry" (Owen Thayer): Two nerds that are sometimes seen at the guys' favorite comic book store. Captain Sweatpants is a middle-aged bald man who wears grey sweatpants and a City of Heroes T-shirt. Lonely Larry wears a brown suit and is extremely thin. They are also friends with Wil Wheaton. Both attend Howard's Batchelor Party.
- Abby (Danica McKellar) and Martha (Jen Drohan): With Leonard and Howard busy on a double date with Penny and Bernadette, Raj and Sheldon attend a university mixer where they meet Abby and Martha. Abby takes a liking to Raj, while Martha tries to connect with Sheldon. While Raj and Abby end up kissing, Sheldon completely ignores Martha, who even tries to go to bed with him. Like series regular Mayim Bialik, McKellar exists within the Big Bang Theory universe independently of Abby, having been mentioned alongside Bialik in ep. 1.13, "The Bat Jar Conjecture".
- Venkatesh Koothrappali (Frank Maharajh): Raj's cousin, a lawyer in India, who tries to negotiate a deal for Raj's part of the One Ring prop from Lord of the Rings. He, by his own admission, is a bad negotiator, and does not get Raj even one of the two JetSkis that Raj wanted.
- Dr. Elizabeth Plimpton (Judy Greer): A renowned cosmological physicist from Princeton University known for her work in quantum cosmology who comes as a personal guest of Sheldon in "The Plimpton Stimulation" episode. She first appears absence-minded, but then exhibits a strong sexual libido, winds up having sex with Leonard and Raj, and expresses a desire for a foursome with Leonard, Raj, and Wolowitz.
- Joyce Kim (Ally Maki): A previously unseen character who appears in "The Staircase Implementation", Joyce Kim was mentioned as a former girlfriend of Leonard; their relationship only lasted a month, after which she defected back to North Korea. However, in The Staircase Implementation, Leonard admits that she was not a girlfriend, but a North Korean spy who attempted to get secrets from him by seducing him.
- Joy (Charlotte Newhouse): An exercise-freak woman whom Leonard meets on a blind date set up by Bernadette via the "Girlfriend Pact" with Howard. Although Leonard finds Joy's personality to be repulsive, he agrees to go out with her again based on hints she gives that it will be easy to have sex with her.
- Special Agent Angela Paige (Eliza Dushku): an FBI agent investigating Howard Wolowitz's background for a security clearance in "The Apology Insufficiency" episode. While interviewing the guys, Raj vomits on her shoes, Leonard hits on her, and Sheldon reveals too much information about Howard, and to add insult to injury reveals too much information about Leonard.
- Wyatt (Keith Carradine): Penny's father. He comes to visit and Penny feels compelled to involve Leonard in a ruse to make him think that they are still together. (Wyatt reveals that he favors the successful Leonard over Penny's other "loser" boyfriends.) When the plot is revealed, he gets mad at Penny and feigns anger at Leonard. But after Penny leaves the room, he encourages Leonard to keep trying to get Penny back (because he does not want his grandkids to "grow up in a house with wheels on it").
- Professor Glenn (Rick Fox): A former professor of Bernadette's, whom she reveals to Howard that she dated for a year. At 6'7", dark and handsome, Glenn is physically the polar opposite of Howard, leading the insecure Howard to feel like he'll never measure up (literally as much as metaphorically).
- President Siebert (Joshua Malina): The president of the California Institute of Technology; he is married and has a teenage daughter. Siebert sends Sheldon on an expedition to the North Pole at the end of Season 2. In Season 4, he organizes a get-together with wealthy donors and faculty in order to garner funds for the university's programs. He urges the guys to make an appearance to schmooze the donors so that they will give to their projects. Seeing Sheldon's behavior toward the donors, he asks that he not appear again. A recurring gag is that President Siebert bumps into Sheldon when he is using the urinal.
- Mrs. Latham (Jessica Walter): A wealthy widowed benefactor who takes a shine to Leonard at a donor/faculty get-together. She asks him out with the implication that he have sex with her in order to get the lab equipment his department needs. He at first resists, but after she says that she is going to fund his project anyway, he relents. Everyone at the University congratulates him for selling himself out for the money.
- Todd Zarnecki (Christopher Douglas Reed): Appears in "The Zarnecki Incursion" episode as a hacker who "steals" Sheldon's possessions in the World of Warcraft online game. Being physically much larger and more intimidating than the four main characters, they back down from confronting him, but Penny sets Todd straight with a swift kick to the groin. He showed up at Howard's bachelor party.
- Emily (Katie Leclerc): A deaf woman whom Penny matchmakes with Raj. Since she is deaf, Raj finds that he can communicate with her despite his selective mutism. She shows interest in Raj when he spends a lot of money on her. Then Raj's parents get the bill, and force him to break up with her. Although Raj resists, he does tell Emily that all the gifts he gave her have to go back. She then loses interest in Raj.
- Alice (Courtney Ford): A good-looking girl who meets Leonard at the comic book store, who thinks he's cute and then has him to her apartment and tries to hook up with him. This date occurs during the period when Leonard was having a long distance relationship with Priya. Leonard initially gives in to temptation, but at the last minute pulls away. He tells Alice about her, that is super power is being a good guy and gets thrown out of her apartment. Next time he's communicating, via the webcam, with Priya, he confesses his weakness. To his surprise, Priya has no problem with it. Upon questioning, Priya reveals that she has not been faithful to Leonard. They then break up.
- Jimmy Speckerman (Lance Barber): a former high-school jock who used to bully Leonard on a regular basis. He later contacts Leonard in "The Speckerman Recurrence", with an idea of inventing glasses that turn all movies into 3D. He is oblivious to the bullying nature of his actions against Leonard, having believed that they were "having fun" and describing him and Leonard as having been "a comedy team".
- Siri (Becky O'Donohue): embodies Siri (software), the voice-recognition system used on certain smartphones and on which Raj developed a crush, because of its sexy female voice. Raj has a dream about meeting her, represented by a stunningly beautiful woman, but he still cannot speak to her in person.
- Spock (Leonard Nimoy): Sheldon's action figure Spock, the voice of Leonard Nimoy, appears to him in a dream convincing him to open his mint in-box 1975 Star Trek Transporter toy. After Sheldon breaks his toy and steals Leonard's, Spock reappears to Sheldon and convinces him to give Leonard his toy back.
Characters that appeared in only a single scene
These characters appear in a single scene. The list is sorted by chronological order of appearance, considering their first appearance in the show.
- Sebastian (Steven Yeun) Sheldon's former roommate who left Sheldon on bad terms. Sebastian makes a single appearance in "The Staircase Implementation", where he tells Leonard to "run fast, run far" from Sheldon. His name is not used in the episode, but is listed in the credits.
- Louie (Ajgie Kirkland) A former occupant of the apartment in which Penny lives. He is a cross dresser whom Leonard mistakenly runs into in "The Staircase Implementation" episode, and who refers to Sheldon as "the crazy guy across the hall". The name Louie is used by Sheldon, referring to him/her as Louie/Louise. Sheldon implies that Louie is a cop.
- Mrs. Fowler (Annie O'Donnell): Amy Farrah Fowler's mother. She appeared in a webcam conversation with Amy and Sheldon in which they lie to her about the nature of their relationship, telling her that they are in a romantic relationship that includes coitus.
- Angelo (Peter Onorati): A barber who substitutes for Sheldon's regular barber, Mr. D'Onofrio, when Mr. D'Onofrio falls into a coma.
Notable guest stars appearing as themselves
- Summer Glau (Season 2, "The Terminator Decoupling"): When the guys travel by train to a conference in San Francisco, they realize Summer Glau (who was in two science fiction television shows, Firefly and Terminator: The Sarah Connor Chronicles) is sitting in the same passenger car. Raj, Howard, and Leonard take turns talking with her. Raj cannot talk without drinking beer (which turned out to be non-alcoholic), Howard is his usual creepy, over-the-top self, and Leonard cannot start a conversation before she has to get off the train.
- Wil Wheaton first appeared in the season 3 episode "The Creepy Candy Coating Corollary". See his entry in the recurring character section for more information.
- Katee Sackhoff (Season 3, "The Vengeance Formulation" and Season 4, "The Hot Troll Deviation"): Howard fantasizes about taking a bath with Katee Sackhoff (Captain Kara "Starbuck" Thrace in Battlestar Galactica). However, in his own fantasy Sackhoff scolds him and tells him to get a real girlfriend instead of imaginary ones. Sackhoff reappeared in a different fantasy of Howard's in The Hot Troll Deviation, where she and George Takei help Howard realize that he still has feelings for Bernadette.
- George Takei (Season 4, "The Hot Troll Deviation"): During one of Howard's fantasies, Takei, along with Katee Sackhoff, help Howard realize that he still has feelings for Bernadette. Takei's real life homosexuality is twice referenced in the episodes: once, when he first appears in Howard's fantasy, Sackhoff asks Howard if Takei's presence implies that Howard has homosexual tendencies, and the second reference occurs when Takei advises Howard about women's love preferences. Sackhoff asks Takei "How would you know?" and he responds "I read."
- Neil deGrasse Tyson (Season 4, "The Apology Insufficiency") Appears as a colleague of Raj. Upon being introduced to Tyson, Sheldon tells him that he (Sheldon) is upset at Tyson's role in the demotion of Pluto from planet status. Initially, Tyson explains that he had no role in the demotion, but later attempts to apologize to Sheldon. Sheldon declines the apology, immediately after he himself apologized to Howard, who declined Sheldon's apology.
- Charlie Sheen (Season 2, "The Griffin Equivalency"): When Raj discovers a celestial body he is very excited about it. At Penny's restaurant, Raj says to the patron at the next table over, "Hey, buddy. I'm going to be in People magazine!"; Charlie Sheen turns around, takes his sunglasses off and says "Yeah? Call me when you're on the cover." (At the time, Sheen was starring in Two and a Half Men, also produced by Chuck Lorre.)
- Analeigh Tipton and Samantha Potter (Season 2, "The Panty Piñata Polarization"): Howard and Raj visit the America's Next Top Model house pretending to be cable television repairmen. Tipton and Potter made appearances, opening the door for Howard and Raj. Tipton greeted Howard and Raj, caught them in a lie as the house does not receive cable television (it receives satellite), but allows them in regardless when Howard "corrects" his error with another lie when he says that they are satellite television repairmen. Potter did not get a speaking role.
- George Smoot (Season 2, "The Terminator Decoupling"): After a train ride to a conference in San Francisco, Sheldon presents his paper to 2006 Nobel Prize laureate George Smoot, and proposes joint research; Smoot abruptly rejects his idea by asking "With all due respect, Dr. Cooper, are you on crack?"
- Ira Flatow (Season 3, "The Vengeance Formulation"): Sheldon is invited to talk about magnetic monopoles on Flatow's radio show, Science Friday. However, Barry Kripke pulls a prank on Sheldon, and Sheldon is publicly humiliated to a nationwide audience. Flatow's appearance was voice only.
- Stan Lee (Season 3, "The Excelsior Acquisition"): When Sheldon has to miss Lee's appearance at the comic book store because he ends up in traffic court after running a red light, Penny tries to make it up to him by taking him to Lee's house, uninvited and unannounced (acquiring Lee's address from Stuart). Lee, not impressed by the unexpected intrusion, sarcastically remarks "why don't you just come in and watch the Lakers game with me?" only for Sheldon, not understanding sarcasm, to rush into the house. Lee, annoyed, decides to sue for a restraining order. When Sheldon announces his "autographed" restraining order to Leonard, Howard, and Raj, he comments it will look great hanging next to his restraining order from Leonard Nimoy.
- Steve Wozniak (Season 4, "The Cruciferous Vegetable Amplification") Dines in Penny's restaurant at the same time that the guys are there. He compliments Sheldon for his "virtual presence device" (using Sheldon's name for the device without having heard how Sheldon calls it) and in turn Sheldon (having previously referred to him as "the Great and Powerful Woz") compliments Wozniak telling him that he ranks 15th on his list of favorite technological visionaries. When Wozniak feigns disappointment, Sheldon tries to console him by stating that the ranking is six places ahead of Apple founder Steve Jobs. Sheldon then tells Wozniak that the Apple II was rather "nifty" and is one of his proudest possessions. Wozniak promises Sheldon that he would autograph the computer if Sheldon brought it to him. In the haste to get the Apple II to Wozniak for signing, Sheldon trips and falls down the stairs, breaking the computer.
- LeVar Burton (Season 4, "The Toast Derivation"): Sheldon invited Burton to a party via a tweet. Upon opening the door and seeing the other guests at the party, Zack, Kripke, and Stuart (who at that moment was wearing nothing but a towel) singing karaoke, Burton leaves and when starting to walk down the apartment block stairs utters that he is "so done with Twitter". Along with Brent Spiner and Wil Wheaton, Burton makes Star Trek: The Next Generation the most represented franchise on the show in terms of guest appearances.
- Brian Greene (Season 4, "The Herb Garden Germination"): Sheldon and Amy attend a book signing event of Greene's popular science book, The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos. At the event, Sheldon initially ridicules Greene in private conversations with Amy, but then he gets up and publicly ridicules Greene, asking Greene why doesn't he do something more useful with his time than write popular science (only to turn around and state he was kidding).
- Brent Spiner (Season 5, "The Russian Rocket Reaction"): Sheldon shows up at a party thrown by his "mortal enemy", Wil Wheaton, only after he hears that Spiner will be there. After Wheaton gives Sheldon a signed, in-the-box Wesley Crusher action figure, Spiner grabs it and opens it, thus putting him on Sheldon's Mortal Enemies List immediately after Wheaton was removed from the list. Along with LeVar Burton and Wil Wheaton, Spiner makes Star Trek: The Next Generation the most represented franchise on the show in terms of guest appearances.
- Mike Massimino (Season 5, "The Friendship Contraction"): An astronaut who appears as a future colleague of Howard, who is set to join NASA's astronaut corp. Massimino reveals that his nickname is "Mass". Howard thinks the nickname is for Newton's second law which states that force = mass times acceleration, but Massimino reveals that "Mass" is simply short for Massimino. Raj and Howard concoct an elaborate scheme to plant a seed in Massimino's mind to give Howard the nickname "Rocket Man" by having Howard set up the song "Rocket Man" as his ringtone on his cell phone, and Raj calling the cell phone during Howard's Skype conversation with Massimino. Their plan is thwarted when Howard's mother shouts to him that he needs to finish his Froot Loops, which triggers Massimino to give Howard the nickname "Froot Loops". He is heard on the phone in "The Launch Acceleration" and seen in the Soyuz capsule with Howard and cosmonaut Dimitri Rezinov in "The Launch Acceleration".
- Leonard Nimoy (Season 5 [voice only], "The Transporter Malfunction"): After Penny buys Sheldon and Leonard each a mint condition Star Trek toy transporter as gifts, Sheldon has a dream in which Nimoy assumes the voice of a toy Spock who convinces Sheldon to open the box and play with the toy transporter. After Sheldon breaks his toy transporter, he switches it for Leonard's. Sheldon then has another dream in which the toy Spock attempts to convince Sheldon to do the right thing and switch them back.
- Stephen Hawking (Season 5, "The Hawking Excitation"): After Sheldon's much-anticipated meeting with Hawking, he discusses Sheldon's research and points out a mistake. Sheldon protests by saying that he doesn't make mistakes, to which Hawking replies "Are you saying that I do?" When Sheldon realizes his research does in fact contain a math error, he faints in embarrassment, prompting Hawking to remark "Oh great, another fainter."
- Yeardley Smith appears in the episode "The Einstein Approximation" as Sandy, a woman in an employment exchange who interviews Sheldon for a prospective job, then flees at the end yelling for "security" after she concludes from his conversation that Sheldon is a nutcase.
- Octavia Spencer appears in the episode The Euclid Alternative (Season 2, Episode 5) as a DMV assistant when Sheldon goes to get a learners permit (the gang want Sheldon to learn to drive as he's always asking them for lifts). After Sheldon annoys the DMV assistant with a number of questions, she gives out Sheldon's Learner Permit without him taking the test in the hope that he leaves.
- ^ a b "The Middle Earth Paradigm". The Big Bang Theory. episode 6. season 1. October 29, 2007. 5:18 minutes in.
- ^ a b "The Vegas Renormalization". The Big Bang Theory. episode 21. season 2. April 27, 2009. 9:42 minutes in.
- ^ a b c "The Luminous Fish Effect". The Big Bang Theory. episode 4. season 1. October 15, 2007.
- ^ "The Guitarist Amplification". The Big Bang Theory. episode 7. season 3. November 9, 2009. CBS.
- ^ "The Electric Can Opener Fluctuation". The Big Bang Theory. episode 1 (41). season 3. September 21, 2009. CBS.
- ^ "The Euclid Alternative". The Big Bang Theory. episode 5. season 2. October 20, 2008. CBS.
- ^ "The Apology Insufficiency". The Big Bang Theory. episode 7. season 4. November 4, 2010. 12:50 minutes in.
- ^ a b c d "The Countdown Reflection". The Big Bang Theory. episode 24. season 5. May 10, 2012.
- ^ a b "The Psychic Vortex". The Big Bang Theory. episode 12. season 3. January 11, 2010. 8:25 minutes in.
- ^ a b c d e "The Grasshopper Experiment". The Big Bang Theory. episode 8. season 1. November 12, 2007.
- ^ "The Middle Earth Paradigm". The Big Bang Theory. episode 6. season 1. October 29, 2007.
- ^ Season 3 Episode 23 The Lunar Excitation
- ^ a b "The Roommate Transmogrification". The Big Bang Theory. episode 24. season 4. May 19, 2011.
- ^ a b c "The Herb Garden Germination". The Big Bang Theory. episode 20. season 4. April 7, 2011. 19:08 minutes in.
- ^ "The Stag Convergence". The Big Bang Theory. episode 22. season 5. April 26, 2012. 07:41 minutes in. CBS.
- ^ a b c "The Creepy Candy Coating Corollary". The Big Bang Theory. episode 5. season 3. October 19, 2009.
- ^ a b c "The Vengeance Formulation". The Big Bang Theory. episode 9. season 3. November 23, 2009.
- ^ a b "The Zazzy Substitution". The Big Bang Theory. episode 3. season 4. October 7, 2010. 5:53 minutes in.
- ^ a b "The Jerusalem Duality". The Big Bang Theory. episode 12. season 1. April 14, 2008.
- ^ "The Bat Jar Conjecture". The Big Bang Theory. episode 13. season 1. April 21, 2008.
- ^ "The Panty Piñata Polarization". The Big Bang Theory. episode 7. season 2. November 10, 2008.
- ^ "The Cornhusker Vortex". The Big Bang Theory. episode 6. season 3. November 2, 2009.
- ^ a b "The Griffin Equivalency". The Big Bang Theory. episode 4. season 2. October 13, 2008.
- ^ "The Lizard-Spock Expansion". The Big Bang Theory. episode 8. season 2. November 17, 2008.
- ^ a b c "The White Asparagus Triangulation". The Big Bang Theory. episode 9. season 2. November 24, 2008.
- ^ "The Vartabedian Conundrum". The Big Bang Theory. episode 10. season 2. December 8, 2008.
- ^ "Big Bang Theory: We didn't anticipate how protective the audience would feel about our guys". Variety. May 5, 2009. http://weblogs.variety.com/season_pass/2009/05/big-bang-theory-we-didnt-anticipate-how-protective-the-audience-would-feel-toward-our-guys.html. Retrieved 2010-03-07.
- ^ "The Maternal Capacitance". The Big Bang Theory. episode 15. season 2. February 9, 2009.
- ^ "The Killer Robot Instability". The Big Bang Theory. episode 12. season 2. January 12, 2009.
- ^ "The Friendship Algorithm". The Big Bang Theory. episode 13. season 2. January 19, 2009.
- ^ "The Toast Derivation". The Big Bang Theory. episode 17 (80). season 4. February 24, 2011.
- ^ "The Flaming Spittoon Acquisition". The Big Bang Theory. episode 10. season 5. November 17, 2011. Event occurs at 11:44. CBS. Sheldon is seen looking at Stuart's Facebook page, where his name is seen to be "Stuart Bloom"
- ^ a b "The Hofstadter Isotope". The Big Bang Theory. episode 20. season 2. April 13, 2009.
- ^ "The Classified Materials Turbulence". The Big Bang Theory. episode 22. season 2. May 4, 2009.
- ^ "The Lunar Excitation". The Big Bang Theory. episode 23. season 3. May 24, 2010.
- ^ The Infestation Hypothesis
- ^ "The Good Guy Fluctuation"
- ^ "Pilot". The Big Bang Theory. episode 1. season 1. September 24, 2007.
- ^ "The Financial Permeability". The Big Bang Theory. episode 14. season 2. February 2, 2009.
- ^ "The Dumpling Paradox". The Big Bang Theory. episode 7. season 1. November 5, 2007.
- ^ "The Loobenfeld Decay". The Big Bang Theory. episode 10. season 1. March 24, 2008.
- ^ "The Pork Chop Indeterminacy". The Big Bang Theory. episode 15. season 1. May 5, 2008.
- ^ "The Cooper-Nowitzki Theorem". The Big Bang Theory. episode 6. season 2. November 3, 2008.
- ^ "The Bath Item Gift Hypothesis". The Big Bang Theory. episode 11. season 2. December 15, 2008.
- ^ "The Dead Hooker Juxtaposition". The Big Bang Theory. episode 19. season 2. March 30, 2009.
- ^ "The Jiminy Conjecture". The Big Bang Theory. episode 2. season 3. September 28, 2009.
- ^ "(#402) "The Cruciferous Vegetable Amplification"". the Futon Critic. http://www.thefutoncritic.com/listings/20100830cbs02. Retrieved September 9, 2010.