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
Revealing mistake: Right after Wendy tries to convince the crowd that Cartman's actual paper was 'Walden' with Cartman's name on it, Stan mentions something about Kyle's mom making tuna fish sandwiches. When he does this, you can kind of see him 'lift' off the background.