Revealing mistake: When Dave and Walley are running with a car, Walley says that he heard some shots. Dave replies that he didn't hear anything, but as you know Dave is deaf, and he reads Walley's lips each time he speaks. In this scene, he wasn't looking at him, but answered. (00:47:45)
Revealing mistake: Dave and Wally are checking into a hotel. Dave is looking down and signing in on the paper while the clerk says to them, "we have a room with 2 queens." Dave (still looking down, never at her lips) looks up and says "Well get them fellas out of there." Dave is deaf and would not have made that comment, seeing that he never looked at her so couldn't know what she said.