sentences:  Guest stars have lent their voices to the show including Jay Leno, George Clooney, Jennifer Aniston, Bill Hader, Robert Smith and the comedy duo Cheech & Chong voiced characters representing their likenesses for the season four (2000) episode "Cherokee Hair Tampons", which was the duo's first collaborative effort in 20 years.The entirety of the Nu-Metal band Korn also provided their voices and likenesses in the season three episode "Korn's Groovy Pirate Ghost Mystery".Characters in the show, according to Parker and Stone, are inspired by people they met when they were kids.