Revealing mistake: When Stan falls into the dug-out at the baseball game you can clearly see the crash mat that he lands on.
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: In the middle of the movie, Roy is flossing his teeth by himself. In the mirror as well as when he turns around, you can see his hand holding the hook, if you look closely. (00:58:33)
Revealing mistake: In the scene where Romeo and Roy snap all the clubs other than the 7-iron, Roy drops his golf ball onto the grass. However, when he hits the ball, a white tee can be seen travelling up towards the top left of the screen. The tee can easily be seen but is much clearer in slow motion.