Almost all of the prisoners in the prison and the prisoners taking place in the riot, were in fact real inmates of that prison, with over 80% of them doing hard time for violent crimes.

Just in case you haven't seen the extras, the man in one of the first scenes in the diner who disappears while reading the paper in the booth is Owen, the same guy that helps them out of the prison at the end, possibly making him some sort of guardian angel for the two? (You have to see the alternate ending though).

This film inspired over a dozen copycat murders, some of which involved imagery and dialogue from the movie. One victim's family even attempted to sue Warner Brothers.

10 minutes into the film the show Mallory's family, Mallory's brother in the film, is really director Oliver Stone's son Shawn.

Director Oliver Stone chose Woody Harrelson for the role of Mickey based on the fact that Woody's real father was arrested/convicted of murder as a hitman. Stone was quoted as saying "I could see that killer instinct in Woody's eyes, and although it scared me, he was perfect for this role."