The Beatles were an English rock band. They have been mentioned in numerous South Park episodes.
An image of The Beatles with Chef appeared in the episode "Chef Aid", in Chef's photo album. In "Jakovasaurs", Mr. Garrison asks the class why American rock and roll artist Chubby Checker left the band in 1972. Obviously, Chubby Checker was never a member of The Beatles, which disbanded in 1970. In "Free Hat", the boys compare Raiders of the Lost Ark being remade to The Beatles changing the White Album every year.
The murder of former Beatle John Lennon is heavily referenced in the episode "The Tale of Scrotie McBoogerballs", in which Butters is compelled to "kill John Lennon" after reading The Catcher in the Rye. Cartman also states his belief that Lennon is the 'King of the Hippies' in the same episode. Lennon's widow, Yoko Ono, appeared much earlier, in the Season 3 episode "World Wide Recorder Concert".
Another former Beatle, Paul McCartney, is mentioned by Mr. Mackey as having popularized the drug LSD along with Lennon in the episode "Ike's Wee Wee". McCartney also briefly appeared in a spoof of Family Guy in the episode "Canada on Strike", in which Peter Griffin sings "La Cucaracha" to him.