20 Things You Somehow Missed In Back To The Future
12. Doc Bribes A Cop

As Doc is setting up the power cables at the clocktower, a nosy cop appears from behind, looking suspiciously at the DeLorean. When Doc says he's conducting a weather experiment, the police officer requests to see a permit. As Doc shows him his "permit", the shot cuts to Marty.
At first, you might assume the scene was edited this way to avoid a minor plothole. How can Doc show the police officer his permit... if he doesn't have one? However, a deleted scene reveals that Doc made the copper stay quiet about his little experiment by bribing him. Okay, that explains how he made the officer go away without incident. So why was the scene cut?
Straight after this exchange, Marty tells Doc he's terrified going on a date with his own mother could mess him up and make him turn gay. Doc misinterprets the meaning of this word and says, "Why shouldn't you be happy?" Obviously, this scene was removed since the director worried it would be deemed inappropriate. (Reminder - The same director thought inserting a shot of a cinema showing Orgy American Style was totally fine.)