Sylvester Stallone gained 40 pounds to add realism to his portrayal of the police officer. He also was only paid SAG minimum wages. By the time that reshoots were required, he had lost the weight again.
Robert Patrick got the part after running into actor Peter Berg and the film's producer and music supervisor, Meryl Poster, who were staying in the same hotel in New York. He got the script and then read for director James Mangold a few days later.
The film was released into cinemas uncut in the UK with a '15' rating, but the BBFC (the British censors) felt they had been too lenient and the same version was upgraded to an '18' rating for video and DVD. The Director's Cut was later passed uncut with a '15' rating.
The trivia item below may give away important plot points.
At the end of the film, when Freddy and Gary are bringing in Murray Babitch to the New York City authorities, there is one shot of Moe Tilden coming out of a building. In this one shot, his mustache is noticeably longer. James Mangold wanted to get a shot of Robert De Niro's character walking out of the building. De Niro agreed to return and appear in the shot, but could not trim his longer mustache as it was required for his character, Louis Gara, in Jackie Brown (1997).