Bart's guitar switches from a left to a right handed guitar between act 1 and 2.
Nelson's shirt and vest switch colors for one shot then back, when he taunts Bart about attempting to play "Polly-Wolly Doodle."
In the final scene, Otto bends a stop sign with the bus, but, in the next shot, the stop sign is straight.
When Skinner is stuck in traffic waiting for an opening and it reaches twilight, the bottom window of the bus door is tinted black.
The final scene where Otto picks up the kids doesn't make any sense. They are all standing out side and get into the bus, implying he is picking them up for school, however the view of the stop sign he ran pulls back to Skinner standing in what appears to be a house; if school was beginning for the day, Skinner would already be at school. If school was over for the day, the kids would have piled into the bus which would have been out front of the school.