PRIMUS is the band that composed and performed the South Park Theme. The frontman of the group, Les Claypool, sings the lyrics. Les Claypool is somewhat a South Park character as well, with a few appearances on the show. He appears in the opening, singing the theme song in most of the episodes of the show from seasons one through four ("Cartman Gets an Anal Probe" to "Do The Handicapped Go To Hell?") He also appears on the intro when the show airs in syndication.
PRIMUS performed "South Park Theme" and "Mephisto and Kevin" on Chef Aid: The South Park Album.
PRIMUS' song "John the Fisherman" was played in the episode, "Guitar Queer-o". While studying the nature of existence, Kyle has a psychedelic experience while the song "Welcome To This World" is played in "The Tooth Fairy Tats 2000".
As they appear in "Chef Aid", PRIMUS can be seen wearing yellow and orange chicken costumes with blue and green round graduation caps. Les Claypool's guitar is pink with green and yellow stripes. The bassist's guitar is black with green trimming and the drummer's drums are white and blue with black trimming.