Continuity mistake: Towards the end of the movie Dave takes Walley's jacket and uses it to help them slide down a cable. Before they slid down, Dave tells Walley to hold on, and Walley asks if they're going to be above the ground. Dave tells him no, and off they go. However, Dave is deaf, and reads lips, and Walley is standing behind him when he asks the question. So how did Dave read his lips if he wasn't looking at him?
Continuity mistake: After escaping from the police station, they go into a building and break a wooden door to come out of the other side. When they first break the door, the broken section is only inches away from Richard Pryor. Gene Wilder says to watch out for it. When Richard Pryor moves it, it's slightly further away than it was before.