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.
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.
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: 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.