They are set on the occupation (and silencing) of the colourful, musical world of Pepperland. The majority are furry, six-clawed creatures, but some are humanoid- albeit with blue faces, and a taller stature.
The Blue Meanies arrive in Pepperland and do everything they can to oppress the place. This prompts one of Pepperland's sailors, the former Commander now newly appointed Lord Admiral "Old Fred" (or "Young Fred" according to the even older Lord Mayor) to fly out in the Yellow Submarine of the title to find the Beatles, who, as musicians, would be able to restore harmony (and indeed melody) to Pepperland. The Meanies, in his absence, cause Pepperland to turn into a very dull and oppressive place, wrought with thorns and thistles.
Later in the story, a Meanie abducts the Beatles' companion, Jeremy Hilary Boob, the Nowhere Man, and we see, when the Beatles arrive in Pepperland, how they have laid waste and petrified the natives. The Beatles find the stored-away instruments and their doubles, the Sgt. Pepper's Lonely Hearts Club Band, and bring music back to Pepperland. This restores colour to the hills and plants and life into the natives (who had been petrified by various weapons in the Meanies' possession). With their spell thus broken, the Meanies cease to have a hold on Pepperland: even their guns start shooting flowers instead of missiles. Those that do not flee are invited by the Beatles to stay and "mingle" and they make peace with their former enemies.
Weapons and species of Meanie
The Common Blue Meanies: These, it seems, are a sub-species of their Chief's origin. They have navy blue woollen-like bodies, domino masks, and Mickey Mouse-ear-like hats (with the exception of the Chief Blue Meanie himself and his sidekick "Max", whose hats look more like Goofy's ears). They have six claws on each hand, and wear yellow-and-orange striped tights (again, the Chief and Max are the exceptions here, as they both wear jackboots with spurs: light blue boot on the right foot, navy blue on the left). They are also able to make their eyes glow so that they can see in the dark, which makes the head resemble a video projector. These particular Meanies carry guns that fire pale-blue jagged arrows which, on contact, drain the victim's colour and petrifies him or her – although it seems to varying degrees or only temporarily, because several victims in the film are seen to cry, smile, or look up, and several natives of Pepperland are seen to back off at the sight of the Flying Glove (see below).
The Apple Bonkers: These are tall, thin Meanies who can walk from hill to hill at a stride, who wear purple tail-coats (with lapels), bow ties and top hats with feathers in them (underneath their hats, they have half bald heads). Their weapons of choice are giant Baldwin apples, which they drop on people's heads and which have the same effect of the jagged arrows. If one can reach high enough, they too can be knocked out by such weapons, as the Beatles later discover (the Beatles' singing is the only way to reverse the effect). When seen closely, their faces bear a near striking resemblance to Abraham Lincoln, where one Apple Bonker sports Mutton chops, another sports a handlebar moustache and curved goatee on his chin and another sports just a moustache.
The Butterfly Stompers: These are wide, bullying Meanies with cat-like faces. They each carry a number on their chest, and for whatever reason they find it entertaining to destroy butterflies. One of them also stomps upon Max's head at the Chief's behest (or possibly mistaking it for a butterfly too.)
The Countdown Clowns: These are tall, fat Meanies whose heads can spin round and round, and who shriek very loudly when ready to attack, or when they feel the need to alert other Meanies. If their noses are pressed, wherever they look there will appear an explosion. They have no hands or arms themselves, however, and so another Meanie has to press their noses for them, often needing to prop a ladder up against them, or sit up on their shoulders when doing so, because they are tall. When the Meanies' spell is broken, they end up simply producing positive words such as "Yes" and "OK" in block capitals when they try to cause an explosion.
The Hidden-Persuader Men: These are large, fat, bald Meanies (although never referred to as such), who are constantly smoking cigars and carrying martinis which appear to have eyes on the glass. These men appear to be harmless, but upon closer inspection, they have an extra hand inside their shoes, which typically wields a pistol and shoots whenever the toe of the shoe is raised. If the shoe is closed at the right time, however, they can be made, quite literally, to shoot themselves in the foot. They are one of the rarest seen Meanies. When the Meanies' spell is broken, we see them clinking their glasses together and using their third hands to shake.
The Snapping-Turtle Turks: Possibly the most pettily cruel of the Meanies, and dressed like stereotypical Turkish men, sporting handlebar moustaches and curved goatees on their chins (they even sport those curved Arabic shoes and fezzes). These are comparatively short Meanies, but are fat, and their stomachs are in fact oversized, predatory faces whose crocodile sharp-toothed mouths consume objects. We see one of these eating a little girl's paper windmill on purpose to make her cry. In their first screenshot (the only time they are referred to by name), the word 'turtle' is not included, which is appropriate, as their stomachs, as said, actually resemble crocodile faces.
The Jack-the-Nippers: These are tall, muscular Meanies who have moustaches, half bald heads and wear green tail-coats and sunglasses and have reptilian heads for hands. Much like the Snapping-Turtle Turks' stomachs, these hands are used for fierce biting (the animals their hands resemble are even the similar animal the Snapping Turks' stomachs resemble, alligators, thus giving them the nickname 'Gator-Handed Men', which they are also known as) but if startled can bite their own tongues, causing extreme pain. They are the least frequently seen of all the Meanies, especially as, much like the Hidden Persuaders, they too are never referred to by name – either 'Jack the Nippers' or 'Gator Handed Men'. The name is a play on Jack the Ripper.
The Four-Headed Bulldog: There is possibly just one of these, but that hardly matters, as it has four heads, each with very sharp teeth. It is extremely strong, and its handler is no match for it if it wishes to walk in a particular direction. It is ultimately defeated when the Beatles and the Sgt. Pepper's Lonely Hearts Club Band, sing "Hey Bulldog" and run in opposite directions to disorientate it.
The Dreadful Flying Glove: The Chief's fiercest and strongest fighter. Though there is only one glove, it is a force to be reckoned with: crushing, squashing, or "o-blue-terating" whoever or whatever its master directs it to attack. It varies from being a right-handed glove to a left-handed one, depending on the situation, has a stylised face, with the thumbnail acting as the eye and the index finger as the nose, the middle finger and ring finger serving as its mouth (grinning teeth are clearly visible between these fingers). As it clenches itself into a fist, it covers up its eye, temporarily blinding it. The glove also has an evil dreadful sounding laugh in a low register. It is ultimately defeated when John sings "All You Need is Love" and covers it with the letters of all the words that spring from his mouth as he sings.
The Anti-Music Missile: This is seen used at the start of the film to initiate the attack on Pepperland. The missile itself if simply a large blue-tinged bubble which is launched from a silo hidden in the Blue Meanies' mountain. It is used to trap Sergeant Pepper's Lonely Hearts Club Band and silence their music. The citizens of Pepperland scream and run in panic when they see the Missile used, suggesting that it is always used by the Meanies to start an attack by silencing the biggest source of Music. The Missile is destroyed by Ringo using the hole in his pocket which frees the band trapped inside.
Mad Mod transformed into a stylised "Union-Jack" Chief-like blue meanie temporarily during an episode of Teen Titans. He did this just after adjusting his rectangular sunglasses, suggesting some kind of hidden shape-shifting ability.
Pro Wrestler, Brian Heffron, uses the ring name "The Blue Meanie" and his hometown is billed as "Pepperland." He also uses face paint to mimic the black outline around the eyes of the animated blue meanies.