Continuity mistake: During the briefing of the American soldiers before the war with the Canadians, watch the background whenever we cut back to the big-general. The soldiers change positions on a fairly regular basis.
Continuity mistake: in the scene where Mr Mackey is teaching the kids not to swear, as he starts his song "It's Easy Mmm-kay", the rose on the piano is on the left hand side. By the end of the song it's on the right. (00:14:48)
Continuity mistake: The first time the South Park boys see the Terrance and Philip movie, their order in their movie theater seats is (from left) Kyle, Stan, Eric, and Kenny. After a couple leave, saying "Well, what do you expect, they're Canadian", a shot from behind shows that Stan and Eric have switched places. In other shots they're in the original positions. (00:05:00 - 00:06:55)
Continuity mistake: In the scene where Mr Mackey is conducting the class on not swearing, we never see Kenny in the scene. Then all of the sudden we see him in the musical number. Where was he before? (00:14:50 - 00:16:10)