Les Claypool is a singer and bassist. He is best known on South Park as the singer of the South Park Theme, composed by PRIMUS. He and PRIMUS also recorded "Mephesto and Kevin" for the Chef Aid: The South Park Album.
Claypool is visible in the original South Park intro, where he is shown walking through the town of South Park, singing and playing a guitar. PRIMUS appears in "Chef Aid" as one of the performers helping out Chef.
He hasn't been shown in the intro since Season Four, as the intro was remixed for "Fourth Grade", but he still sings the theme song, which has been remixed three times: originally for "Fourth Grade"; a country-like remix used at the beginning of Season Six and ending in mid-Season Ten; then remixed from there, using the song "Whamola" from Frog Brigade's 2002 album, Purple Onion.
Aside from the intro, he has appeared a few times in the show itself; otherwise, he is not referenced in any way whatsoever. He is one of the few celebrities that has not been parodied. Claypool's appearance on the show is distinct, his South Park counterpart is typically shown with a red long-sleeved shirt, blue jeans, purple socks, and blue shoes. He also wears a white hat with a yellow trim, sunglasses, and he has facial stubble.