"I'm Looking Over a Four Leaf Clover" is a song from 1927, written by Mort Dixon with music by Harry M. Woods. It was a hit for Art Mooney & His Orchestra in 1948 and was largely popularized by him. In modern times the song is perhaps most associated with Merrie Melodies cartoons, as it appeared in several of them. The Sons of Ben, the official supporters' group of Major League Soccer's Philadelphia Union, have adopted the song as one of their chants, singing at every home match at the 20 minute, ten second mark, symbolic as the founding year of the Union.
In 1948 Columbia records released a recording of the song by Tiny Hill and the Hilltoppers.
The UCLA Band has played an arrangement of this tune since 1954, and uses the chorus as the second part of Rover, the Bruin victory song. Similar lyrics have been used for two other songs.
My Dead Dog Rover by Hank Stu Dave and Hank (Hank Landsberg & Dave Whited) from 1977, which appears on the Dr. Demento 25th Anniversary Collection - The parody version "I'm Looking Over my dead dog rover" was played on Dr. Demento's show for a time.
I’m Lookin’ Over My Dead Dog Rover by Kevin Gershon from 1973 and played on KMET FM in Los Angeles
Also in 1948, Al "Jazzbo" Collins, a popular Salt Lake City disk jockey, is credited with popularizing Art Mooney's version of the song after he pulled a stunt playing the song over and over for hours on end. Some sources state 3 1/2 hours, other say it was 24 hours. For 120 minutes Mooney played on while phone calls poured in from pleased listeners who added insult to Collin's injury by praising him "for playing something good for a change." 
In the 1952 cartoon Operation Rabbit, Bugs Bunny sings "I'm looking over a three leaf clover that I overlooked bethree."
In the 1957 cartoon Ducking the Devil, directed by Robert McKimson, the Tasmanian Devil escapes from a zoo; Daffy Duck, on learning that there's a $5,000 reward for its return (and that the escapee is lulled by music) ends up singing to get him back to his cage. I'm Looking Over a Four Leaf Clover is one of the songs he sings.
In the 1959 cartoon Backwoods Bunny, written and directed by Robert McKimson, Bugs Bunny sings the first two lines of the song, stressing the sound four as that is the given signal for Elvis Buzzard to fire his rifle.