Other mistake: All the Hippies have spent a week smoking weed. Yet Stan, Kyle and Kenny, who have been with them, are not affected by the passive smoke. (00:18:00)
The Mexican Staring Frog of Southern Sri Lanka - S2-E6
Visible crew/equipment: When Jesus was talking his mouth did not move. (00:19:41)
Plot hole: When Cartman is 'confessing his love' to Kyle at the basketball game, the crowd all turn to Kyle and say "Awww" to him. By the time the crowd turn to Kyle, all Cartman had said was that he loves Kyle. No image or live footage of Kyle was ever shown by that point, so how would anyone in the crowd have known who Kyle was or where he was even sitting?
Continuity mistake: The level of beer in people's glasses never changes. (00:11:35)
Mr. Garrison's Fancy New Vagina - S9-E1
Continuity mistake: In the doctor's office, Kyle's facial expression changes completely and instantly. (00:07:30)
Continuity mistake: In the opening the boys get on the school bus. Stan is on the fifth row, Cartman is on the sixth row, Kyle is on the seventh row and Kenny is on the eighth row and there are another two rows behind them. But in the shot after Cartman says "Ample parking day and night! People shouting howdy neighbor!", Kenny is now on the back row. (00:00:10)
Clubhouses - S2-E12
Plot hole: When Roy gets caught in Stan's bear trap, he is seen hanging in front of the clubhouse. Yet the next day, when Stan, Clyde, Bebe and Wendy are playing Truth or Dare in the clubhouse, Roy is not shown hanging outside the clubhouse anymore.
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