When Homer goes to Moe's, he is walking. But when he leaves, he is driving.
When Lisa's hamster is on the hot wheels track it goes down the top steps yet in the very next scene it goes down the same steps again.
When Stephen Hawking is explaining the black hole lens theory, on how Bart did not see Ray Ray Romano talking to Homer in the store earlier in the episode. Bart walks in from the right side in front of Homer. In the previous scene with Homer and Ray, Bart walks in from the left.