Lenny Montana, the actor who played Luca Brasi in The Godfather was actually a member of the Colombo crime family sent to monitor the set. Coppola cast him, but due to his nerves, he kept making mistakes and repeating his lines to himself. This was then incorporated into the film as a character.
The filming of The Godfather faced strong opposition from the Italian-American Civil Rights League, with disputes headed by Joe Colombo and Frank Sinatra threatening its whole production. Producer Al Ruddy eventually made a deal with the league and Joe Colombo to cut the word Mafia from the script, and the league would back the production of the film. This meant many mobsters would be present on the set of The Godfather. It was in 1971, when Montana was acting as a bodyguard for a senior Colombo Family member, that he met Francis Ford Coppola and Al Ruddy. After being introduced to the 6-foot-6, 320-pound Montana, they quickly cast him for the role of Luca Brasi. When Bettye McCartt, Al Ruddy’s assistant, broke her watch, Montana offered to get her a new one. A week later, Montana returned with a “gift from the boys” – an antique diamond watch. He was picked for the part after the original actor playing the character died of a stroke. This would be his first film appearance. His role was that of mob enforcer Luca Brasi, a hitman used by Don Corleone (Marlon Brando). Montana was very nervous about appearing opposite Brando. Director Coppola incorporated this real-life tension into several scenes, showing Brasi repeatedly practising (and later fumbling) his congratulations to Corleone. Montana had little screen time in the film, but his notable height and physique caught the eye of producers, and he appeared in several movies and television programs after appearing in The Godfather.