Continuity mistake: When Bart uncovers the photo of the Simpsons behind the books in Lisa's locker, the books change between shots.
Continuity mistake: After Bart cleans his hands with a cloth after going to the private toilet, he puts it on his shoulder. A couple of shots later it has disappeared.
Other mistake: When the pupils are doing the test at school, you hear Miss Hoover say a question with three possible answers; but 1) There are 5 possible answers on the test when we see Lisa doing it, and 2) Miss Hoover says the 60th question, but Lisa looks to be nowhere near the 60th question.
Deliberate mistake: Lou and Eddie are driving Bart around in the cop car. Bart asks when they're going to shoot people. The shot cuts to Lou, who is driving. The entire frame of the car disappears around him and it's just him superimposed over a background. The shot cuts again and the frame is now visible. Even if it was a low-angle shot, you'd still see the roof of the car.
Continuity mistake: When Dolph and Kearney give Milhouse a "wedgie", they are both shorter than usual.
