Banned in China: It's illegal to own a copy and/or import the video game in New Zealand. Australia also banned it.
Cast the Expert: Mr. Blue, a member of the gang who only shows up in two scenes is played by Eddie Bunker, a real life former criminal and convicted felon before he went into acting and writing crime fiction.
Mean Character, Nice Actor: Michael Madsen had difficulty filming the torture scene, but when the actor playing the cop ad-libbed the line about having a child, he flat-out refused to continue until the next day. This moment actually crosses over into the film itself; on some DVD releases, after the line is spoken, Madsen can clearly be heard breaking character and murmuring "Oh no, no," from off-screen.
Throw It In: Everything after Mr. Blonde cuts off the ear was ad-libbed by Michael Madsen.
In his Hot Fuzz commentary with Edgar Wright, Tarantino reveals the gesture Mr. Brown makes at the end of the opening scene is not from the character at all, but Tarantino the director, telling everyone to just leave after finally getting a good take out of Lawrence Tierney.
Tarantino was originally just going to write and act in the film — the person he actually wanted to direct was Monte Hellman, who had directed some cult films way back in the '60s and '70s, but was way past the best of his career by that stage - his last film had been the abysmally poor Silent Night Deadly Night III Better Watch Out, for perspective. A Hellman-directed version of Reservoir Dogs might not have been a total disaster, but it's hard to see it being anywhere near as good as what we ended up with. Fortunately, Tarantino eventually summoned up the courage to direct the film himself.
Samuel L. Jackson auditioned for the role of Mr. White — being cast as Jules Winfield was a favor for not getting the part. One would expect that the naming scene would have included some objections over a black man getting the name Mr. White.
Tarantino wanted James Woods to act in the film, but Woods' agent turned it down... without consulting Woods himself, for which he was fired. It's not clear which role Tarantino had in mind, though most fans suspect it was Mr. Orange.
Timothy Carey was considered for the role of Joe, and evidently liked the script a great deal. Reasons vary as to why he was not cast. On one DVD extra, Tarantino (who dedicated the Dogs script to Carey, among others) claimed that he felt the famously difficult to direct Carey would have been more trouble than he was worth, before admitting that "Timothy Carey at his worst could not possibly have been more difficult than Lawrence Tierney." Another story holds that Carey auditioned, but was vetoed by Keitel, acting in his capacity as producer.
David Duchovny auditioned as well. According to Duchovny, Tarantino told him "I like what you do, I just don't know if I want you to do it in my movie."
Word of God: Tarantino says that the briefcase from Pulp Fiction was originally supposed to have contained a cache of diamonds before Tarantino decided that keeping the contents of the briefcase ambiguous made it more interesting. Since Pulp Fiction and Reservoir Dogs take place in the same universe (Vic and Vincent Vega, major characters in both films, are brothers), it's been theorized that the briefcases in both films are actually the same briefcase, which would mean that someone in the criminal underworld sold the diamonds to Brett and his gang before the police could return them to their rightful owners.