In "Tweenlight", when the families are done eating, there is still half of Flanders' body left. Homer asks a couple of questions and when we see the table again a couple of seconds later, the whole body is gone.
When Homer and Bart are carving pumpkins in the opening sequence, the door is closed. In the next shot, the door is opened and is facing the opposite side. In another shot, the door is facing the right way.
When all of the evil board games are approaching Bart, he manages to run back to Mouse Catch without having to swim over it again in a previous shot.
In "Tweenlight", Dracula mentions that when Lisa becomes a vampire she'll be immortal, so Edmund is too since his father said "you'll both be eight forever". However he later says to Homer that he remembered Edmund from a baby, sleeping in the daytime and checking he was still not breathing. How then can Edmund be a vampire from a baby if a vampire doesn't age?