Other mistake: In 'Homega man', Homer goes into the bomb shelter and does not shut the door, and you can still see it open for a while after he is in there. Herman does not close it behind him - you can tell by his skeleton's position. But Homer opens the door to leave the shelter after he has eaten the food, and it must have been closed for him to have survived the atomic attack, because it vaporised Herman, who was only a few feet away.
Continuity mistake: When the family are walking through the car park after the visit to the Knowledgeium they walk by a purple car and there is a quick visual of a blue car in the bottom left hand corner of the screen.They immediately stop and they are now next to a pink and brown car.
Continuity mistake: When the Simpsons are spying on the old man, the boy and the old woman, all three of them disappear and then reappear between shots. Whenever there is a wide shot from outside the house, they are not there but when there is a close shot from outside or inside they are there.
Continuity mistake: In "Krusty Gets Busted", Krusty's natural skin colour is established as yellow. In "Brush With Greatness" we see him wiping off the clown makeup to reveal that he has yellow skin. But in "Homer's Triple Bypass", he comes to visit Homer, with his white clown face, and tells him that "this isn't make-up". Other episodes after that also show that his skin is white...