According to the Blu-ray behind-the-scenes information, the ending exposition was running over six pages, and the writers realized that would take far too long. Richard Gere and Edward Norton began to improv with it, encouraged by the director and writer, and pared the scene down to less than two pages with a much crisper ending.
Both Wil Wheaton and Leonardo DiCaprio turned down the part of Aaron Stampler. Wheaton turned down the role because he did not want to put off his acting school, and when his manager urged him to take the role anyway, he told him, "It is like Luke Skywalker when Yoda told him not to go and save his friends, but to stay on Dagobah and learn to be a Jedi instead. Luke didn't listen to him and that's why he never became true Jedi master." Later, Wheaton regretted turning this role down, saying that this was a crucial factor why his career never got to be a successful one.
According to the Blu-ray behind-the-scenes information, the original rough cut of the film ran for three hours and fifteen minutes, including more detailed exposition of Aaron's small-town country life and discussions with his former junior high school teacher. The scenes were cut partly for running time and partly to avoid the producers "tipping their hand" and alerting the audience to the ultimate ending.
Both Richard Gere and Reg Rogers, the actor who plays the journalist Gere talks to throughout the movie, were in Runaway Bride (1999). In that film, Gere was the journalist and Rogers was the interview subject as one of the grooms left at the altar.
The exterior police station where Martin Vail goes to see Aaron Stampler is the same exterior police station used for the TV series Hill Street Blues (1981) , for which director Gregory Hoblit was producer and director.
The trivia items below may give away important plot points.
According to the Blu-ray behind-the-scenes information, it was Edward Norton's idea to stutter as "Aaron," as it appeared nowhere in the original book or script. In addition, when "Roy" shoves Vail (Richard Gere) against the prison cell wall, Gere's shocked reaction is genuine, as that was another ad-lib by Norton. Another Norton ad-lib was Roy's slow clap at the end just before the exposition when Vail realized what had happened.
According to the Blu-ray behind-the-scenes information, a second ending was considered during which Marty Vail would get Aaron/Roy back into court and justice would be done, vindicating him. The idea was scrapped in favor of the egotistical Vail getting outsmarted by what appeared to be a dim country hick.