Corrected entry: Right before Cynthia comes over, Jack is looking into the mirror and getting ready. He picks up a gun shaped hair dryer and starts drying his hair. However his hair was already dry to begin with.
When Randy Quaid is trying to make the shot on the giant windmill, he swings and hits the ball. You can see the ball flies almost vertical and way to the right of the windmill. However the next shot shows it landing right on target.