Continuity mistake: Near the end of the movie during the final round of golf Happy is wearing a tee-shirt under a button shirt that is open. All through the round the tee-shirt goes from a Subway shirt to a white shirt with a brown strip across the chest. It is much more noticeable during the last putt. He has the stripe shirt while putting then when he makes it and every one rushes to him it is the Subway tee-shirt.
Continuity mistake: At the beginning when he enters the apartment he barges through the door leaving it open but when the lady walks in she has to open the door.
Continuity mistake: During the segment where the V.W. bug hits the media tower there are a few inconsistencies. First off when the bug hits the tower the pole wraps around the front end staying intact. In the next shot it shows the pole is broken and sitting on the hood. Then there's a shot where it shows a guy laying on the ground and the bug in the background. Now the bug has backed up about 4 feet and the pole is now not broken and only bent. (01:14:18)JamesP
Plot hole: The bet between Happy and Shooter is in no way legally enforceable. Even if it was legal to make such a bet and it have it be enforced, the only person who can verify it was ever even made is Virginia who's obviously biased as Happy's girlfriend. The only way Shooter would actually honor the bet is to keep his word, which is completely out of character (he is the bad guy after all). And I'm sure with the money he's earned he can hire a bodyguard to protect him from Mr. Larson.