Continuity mistake: In the classroom scene where Kyle tries to be excused from class to find Ike, Cartman sets Pip on fire as he was sitting just behind him to the the left. However in the previous shots Pip had not been sitting there, some other kid was and wouldn't have had enough time between shots to move.
Continuity mistake: After Mr Garrison announces Kathie-Lee will be presenting an award for Cartman, you see the next scene in the Mayors office. There we can see cleary the curtains are red, then she looks out the window and looking in the office from outside, they are pink, but it goes in the office again and now they are back to red.
Add timeA Demon
Continuity mistake: In the episode "Cat Orgy" when Sheily's boyfriend, Sklar, are playing the song for Sheily while Cartman is hanging on the coat rack you can see of what looks like a picture of Cartman's grandparents hanging on the wall. But when Sheily walks over and flings Cartman up into the ceiling for arguing with her, look at the wall, the picture is completely gone.
Continuity mistake: When Eric comes running over to talk to the other 3 boys about the handicapped competition, their toy trucks are quite far apart from each other, but when it cuts from Cartman and then back to the boys, Kyle's truck has moved all the way in front of Stan's truck.