Tipping Point
Steve Buscemi said that he had to over-tip in restaurants after the movie was made, to compensate for his character's unwillingness to tip. People thought he was actually like that in real life. (Source.)

It Won't Ever Be on Network TV.
Reservoir Dogs has the fifteenth highest "F" word per minute count of all movies. There's a total of 269, averaging 2.7 per minute. That Tarantino has quite the mouth on him. (Source)

Art Imitates Life
Lawrence Tierney was apparently a pretty tough character in real life, arrested many times while drunk for assault and disorderly conduct. In an interview with his nephew Tim Tierney, Tim recalls that Lawrence, during an off day of filming Reservoir Dogs, "tried to shoot my cousin (his nephew) Michael and ended up doing some time at a prison camp for it. Tarantino said, "he was taken from his bail arraignment to the set." (Source)

Now That's What We Call Method Acting
Kirk Baltz (who played Marvin Nash), asked Michael Madsen (Blonde) to drive him around in the trunk to get into character. Madsen said, "After he got in I drove around the neighborhood for a little while because I then realized it was a good idea for me also to get into character. I don't think he appreciated it so I had to later remind him it was his idea." (Source)