Revealing mistake: While Hayley is throwing up into the bin, you can hear the sound of it going into the bin. However, you can see nothing is actually going into the bin while she is doing it.
Revealing mistake: When Stan is at the launderette, a man is shown writing on paper. There is no ink shown on the paper. He's also only writing on one single line and not moving down after finishing the line. (00:01:10)
Revealing mistake: When Stan comes home and starts talking to Francine, as Francine is saying "You're just having a mid-life crisis", there are three objects in the background that are cut in half and seem to be floating in the air. (00:02:10)
Chosen answer: The Beat.
MasterOfAll