Continuity mistake: When Bart gets on the bus, we see one of the twins sitting near the front of the bus. In the next shot, we see both twins sitting at the back. The shot after that, we see the twin near the front again, running to the back.
Continuity mistake: When Homer gets turned into a jack-in-the-box, we don't hear the chair he was just holding crash onto the floor. Bart doesn't make it vanish, as we see it on the floor when Homer is turned into a jack-in-the-box.