Banned in China: In late 1994 the film was banned from theatrical distribution in Ireland. The Irish Film Centre, which is a membership club and not subject to the same rules as public theaters, booked the film and had it scheduled to screen for a month long run in early 1995. The film censorship board threatened legal action if the film was shown, and it was withdrawn.
Bowdlerize: Stone was forced to cut three minutes of graphic violence at the behest of the MPAA and the studio in order to achieve an R-rating. All of the footage was restored a few years later for a Director's Cut VHS and Laserdisc. In his introduction to the Director's Cut, Stone says he felt that some of these edits done for the theatrical version made the film more disturbing, as some of the censored footage was played such an over-the-top manner that its intention as a satire became more pronounced.
Irony: This is one of the few moments of the (uncut) movie more-or-less faithful to Quentin's original script. Doubly ironic when you realize that Quentin himself had only written this scene because the real-life bodybuilders on whom the Brothers are based had been interested in funding the film (long before Quentin had sold the script off), on the condition that they'd have a cameo… and that, therefore, Quentin wasn't particularly fond of the moment.
Denis Leary and Ashley Judd had cameos that were cut, the former as a ranting prisoner and the latter as a trial witness.
Dyeing for Your Art: Oliver Stone wanted Juliette Lewis to bulk up for the role of Mallory so that she looked tougher, but Lewis refused, saying she wanted the character to look like a pushover, not like a female bodybuilder. In the end, Stone agreed, but he insisted she take kick-boxing lessons so that she looked credible when fighting.
Mallory's line to Scagnetti about him being "so specific" when he asks her to pinch his nipple was improvised by Juliette Lewis on set.
Lewis improvised much of her dialogue, a fact which annoyed Robert De Niro when he found out, as he felt she was disrespecting the film's writers.
Wag the Director: Very little of this film is derived from Quentin Tarantino's screenplay. Tarantino says that the only aspect of the film he'll acknowledge as being his are the character names Mickey and Mallory.
As this Cracked article points out, had Tarantino directed and used his original script, the film could well have been a phenomenal success and, combined with Reservoir Dogs, launched his career years earlier. Michael Madsen has commented that, had Tarantino retained ownership of the project, he would likely have starred as Mickey.
When putting together the music for the film, Oliver Stone and soundtrack producer Trent Reznor both wanted to get Snoop Dogg involved, but Warner wouldn't allow it, as Dogg was on trial for murder at the time.
Michael Madsen was initially considered for the role of Mickey, but Warner Bros wanted somebody less intimidating, and with a softer persona, as they felt this might alleviate the brutality of the character somewhat. Brad Pitt was also considered.
Steve Buscemi and Tim Roth were both offered the role of Wayne Gale and turned it down. Jane Hamsher claims in her book about the movie that they did so because Quentin Tarantino told them he would never cast either of them in any of his movies again if they took the role. John Cusack also passed on it.