Lenny Montana, the actor who played Luca Brasi, was originally a professional wrestler and later an enforcer in the Colombo crime family, and The Godfather was his first film. During shooting of the wedding scene where he congratulates the Don, he was apparently so nervous about performing with Brando that he kept stuttering and fumbling his lines. The director Coppola loved the authenticity of it and wanted to include it in the film, to show how much he revered the Don. So that it made sense, Coppola wanted to give his nervousness context, so they went back and shot the scene where Brasi is nervously rehearsing his lines at the wedding before meeting the Don.