Continuity mistake: When Happy is trying out for the hockey team, he sends a slapshot in front of the coaches and it breaks the glass. In the next shot the glass is intact.
Continuity mistake: In the beginning of the movie he is not taken onto the hockey team. After he is hustling at the driving range he goes to toughen up. As he is toughening up, Chubbs unplugs the machine. The kid tries it, but he never plugged it back in and the machine still manages to work.
Other mistake: During the last tournament scene at the beginning of it look at the Media Tower the crashed V.W. is already there but that part has not happened yet.
Revealing mistake: In at least one scene, you can see the ruts that the filmmakers made in the greens to make Happy's putts go where they wanted them to.
Revealing mistake: When Happy tosses the IRS agent out of Grandma Gilmore's window, he falls down the steps outside and it is blatantly obvious that he is wearing kneepads under his suit pants.
Revealing mistake: In the scene where the Volkswagen is driving on the golf course to run over Happy, you can see tracks in the ground where the car had already been.
Plot hole: In the final tournament when Happy is stuck in the rough, he swings five times. Assuming he hit his drive into the rough and hit an AMAZING shot from the edge of the water into the hole, he still could do no better than a seven on the hole. Happy only lost one stroke on the hole.
Continuity mistake: The exact same shots of the golf ball sailing through the air are used two or three times, especially during the last golf tournament.
Continuity mistake: When Happy pleads with Chubbs to take him for lessons, he shakes Chubbs' hand. He pulls off a few fingers, but not his ring finger. When the shot changes to behind Chubbs, you can see that his ring finger is not there.
Continuity mistake: When Happy is about to putt and the tower starts to fall, his caddy is behind him. In the next wide-angle shot, his caddy is in front of him, or at least between Happy and the hole, where before Happy was between him and the hole. A couple of shots later, when Virginia runs up to Happy, the caddy is back to his old position again.
Other mistake: When Happy hits the ball in the alligators mouth, he is on the complete other side of the lake where the gator is located, and there is a crowd of people blocking his view, but somehow he can still see through the people and over the lake, to notice the gator taking his ball.
Continuity mistake: After Happy gets hit by the car he's lying on the ground and you can see he's only wearing the Subway shirt. But when he tees off near the end he's wearing a shirt over the subway one.
Continuity mistake: When the alligator takes off with Happy's golf ball in his mouth, he takes off and slides down into the pond where he goes through a patch of water-lilies. When Happy dives in the water after the alligator there are no water-lilies.
Continuity mistake: Happy and his new caddy are discussing the shape of the green and the caddy says the green is slanted to the left. When Happy tells him it only seems that way because he's missing a shoe, the caddy is standing with his feet shoulder-width apart. When the camera cuts to the close-up of his feet, they're together, yet the caddy didn't move.
Continuity mistake: When Virginia and Happy are dancing on the skating rink, when the camera is zoomed in on them, Virginia is holding the hockey stick. Then when the camera zooms out, look closely and you can see she isn't holding the stick.
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.
Plot hole: During the scene when Happy is being reprimanded in Doug's office for the fight he had with Bob Barker, why is it that Shooter is permitted to be in this meeting? It would seem that only Doug, Virginia and Happy should be present as it is none of Shooter's business.
Continuity mistake: When Happy wins at the end, people start running towards him. One of these people is a girl with a blue shirt. Then there's a shot of cheering people that are standing to the side without running to Happy, including Richard Kiel, and the girl with the blue shirt