The closing argument by Edward Norton was taken verbatim from Alan L. Isaacman's actual closing arguments. Isaacman revealed this in a documentary of the film.
Gastrolle: [Larry Karaszewski] the hand that puts a dollar bill in the swimsuit of a lady when the words "20 Years Later" are written onscreen at the beginning of the movie belongs to one of the writers.
Gastrolle: [Scott Alexander] Client #3 sitting at the bar at the beginning of the movie/
According to Rev. Jerry Falwell and contrary to what we see in the film, he did not find out about the parody ad in "Hustler" from his staff at Liberty University. He was alerted to the ad when someone in the media asked him about it.
The character of Doug, one of Larry Flynt's bodyguards in the movie, was bodyguard for the real Flynt at the time the movie was filmed.
The character of Dr. Bob is played by one of the real doctors who took care of Larry Flynt.
The character of the Hollywood judge Thomas Alva Mantke is actually a composite character of many judges, the screenwriters chose to name him after one of their friends.