Brad Pitt, who was a big fan of Lock, Stock and Two Smoking Barrels (1998), approached director Guy Ritchie and asked for a role in this film. When Ritchie found Pitt couldn't master a London accent, he gave him the role of Mickey the Gypsy.
When Guy Ritchie told Brad Pitt that he would be playing a boxer, Pitt became concerned because he had just finished shooting Fight Club (1999) and did not want to play the same type of role again. Pitt took the role anyway because he wanted to work with Ritchie so badly.
Brad Pitt's character and indecipherable speech was inspired by many critics' complaints about the accents of the characters in Lock, Stock and Two Smoking Barrels (1998). Guy Ritchie decided to counter the criticisms by creating a character that not only couldn't be understood by the audience but that also couldn't be understood by characters in the movie.
Every mistake that Sol, Vincent and Tyrone make were inspired by various late-night TV shows about real-life crimes gone horribly wrong.
When Vinny and Sol are sitting outside Brick-Top's Bookies, about to give him the diamond, the man that approaches the car is not really Bullet-Tooth Tony, it was a look-alike. Vinnie Jones didn't show up for shooting that day because he was in jail for fighting the night before.
Guy Ritchie: In the back of the bar when we are first introduced to Doug The Head. Ritchie is the man reading the newspaper.