Continuity mistake: At lunch, two boys exchange Bart's sandwich for a grape. When they give him the grape, it lands in Bart's right hand but in the next shot he has it in his left hand, and when one boy gives Bart a cup, the grape is back in his right hand again, and in the shot after that, the two items have changed positions.
Continuity mistake: This is a mistake for the introduction from seasons 2-20 (1991-2009). When Homer screams, he turns round. You see this in a wide shot. There are no boxes to the right of the door in the garage. However, two just appear out of thin air when he runs through the garage. (00:01:50)