Continuity mistake: In the scene where Tom Green has the boy hanging from a rope with a chainsaw. When the boy cuts the limb the limb hits the car, and bounces onto the ground. The camera cuts to Tom Green and Jason Lee, and then back to a shot where you can see the car and the limb is back on the trunk.
Deliberate mistake: When John and his sister Patty are watching the old videos, it shows John saying that he would pay for his niece's college education and the camera is showing them from the side. John says "And that's a promise from your uncle John." and the camera is in front of him showing his face. There is no way they could change camera angles like that in a home movie.
Continuity mistake: The scene where Jason Lee tells Tom Green to break a window at Jason Lee's workplace. Tom Green tries his hardest to break the glass and we continuously see the dog trying to get out of the office. If you look closely you can see a desk that changes positions - it even covers the dog to where you can just see his head.
Continuity mistake: When Tom Green is trying to break a window to make it look like someone broke in, he uses several chairs to break it, but has trouble. One of the chair he throws bounces off and hits a mannequin and knocks it down. A few minutes later,(during a shot from the outside through the window at Tom Green), the mannequin is once again standing. Then it goes back to being knocked down once again.