Contrary to reports in the news media, Columbine High School is not located within the city of Littleton, Colorado. Littleton is actually the mailing address of the school, not its actual address, which is four miles west of the Littleton city limits in unincorporated Jefferson County (still the suburbs), and is part of Jefferson County Public Schools, not Littleton Public Schools.
The Willie Horton ad from the George Bush-Dan Quayle campaign shown during the film is actually two separate ads spliced together. The footage was removed from the VHS version of the film, but not the DVD.
The trivia items below may give away important plot points.
After Charlton Heston abruptly ended the interview, Michael Moore and his film crew walked down Heston's driveway to find themselves temporarily trapped as the gate closed. Fearing that Heston may have called someone to try and confiscate the interview footage, Moore had his cameraman pass the film through the bars of the gate to staffers waiting outside. Moore then told the staffers to depart immediately with the film. Moore and his crew eventually left Heston's estate without incident.
After two years of trying to get an interview with Charlton Heston, Michael Moore was going to give up. Showing up at Heston's house was totally spontaneous--on the way to the airport, a staff member suggested that they buy a "Map to the Stars' Homes" to find the house.