Terrance & Phillip in 'Not Without My Anus' - S2-E1
Trivia: This episode aired the day "Cartman's Mom is Still a Dirty Slut" was supposed to air. Since it was April Fools Day, the creators decided to play a prank by airing this episode. This resulted in Comedy Central getting phone calls from angry viewers who hated how they had waited four weeks for the identity of Cartman's father to be revealed only to discover that they had to wait an additional three weeks for the actual episode. Consequently, this episode was shown again on Comedy Central only twice. The second being right before the release of the movie.
Answer: He appears in at least 5 other episodes, but usually just as a background character. He can be seen at Cartman's party in "Immaginationland". He was also one of the kids trying out to replace Butters in the "Professor Chaos" episode.
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