Continuity mistake: When Happy and Bob Barker are fighting they roll down the hill, just as it appears that Happy wins the fight Bob grabs him by the throat. Bobs pants have a small wet stain on the butt area. After he hits Happy and walks away the wet spot is the whole area of his butt.
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.
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.
Continuity mistake: In the final round, when Happy and Shooter McGavin are about to tee off on the first hole, they show a picture of the 18th green with the Volkswagen Beetle already crashed into the TV tower. However, this doesn't happen until Happy gets hit by the car later in the game.
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.
Continuity mistake: In the final golf scene at the 18th hole, the media tower falls in front of Happy's ball. When he decides to use the tower to help his ball go in the hole, watch the heads of the members of the audience. Happy hits his ball and the members of the audience are watching the ball and following it as it makes its way down the tower. It is natural that their heads will go left, right and down as they follow the ball. However, a few times, it is shown that their heads even go up, as if they are following the ball upwards. Clearly nothing can naturally move up on its own. Plus, it's only shown that the ball is going down, or to the sides.