Audio problem: Just before Kenny explodes from eating all of Mr. Broflovski's antacid tablets, we hear Kyle, Stan and Cartman shout out Kenny's name. One problem - Cartman isn't in the room with them. He isn't even on their debate team. (00:10:35)
Something You Can Do With Your Finger (a.k.a. Fingerbang) - S4-E8
Audio problem: After the first group of people run to buy an orange smoothie, when the security guard says, "Jesus, they're gonna start a riot," his mouth never lip-syncs the word "riot." (00:08:28)
A Very Crappy Christmas - S4-E17
Audio problem: The animated Christmas movie the boys are making is really "the Spirit of Christmas", the movie Trey Parker and Matt Stone made before South Park. The dialogue recorded by the boys is the same as in the original (with a few changes, but when the film is shown later it's the original speech from "The Spirit of Christmas". You can tell by the way the voices are done, and the tone of the voices.
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.
Bishop73