The three-year-old child actor Anthony Gounaris responded best when his real name was used while shooting the film. That’s why Michael’s son’s name is Anthony.

The cat held by Marlon Brando in the opening scene was a stray the actor found while on the lot at Paramount, and was not originally called for in the script. So content was the cat that its purring muffled some of Brando’s dialogue, and, as a result, most of his lines had to be looped.

During rehearsals, a false horse’s head was used for the bedroom scene. For the actual shot, a real horse’s head was used, acquired from a dog-food factory. According to John Marley, his scream of horror was real as he was not informed that a real head was going to be used.

Marlon Brando wanted to make Don Corleone “look “like a bulldog,” so he stuffed his cheeks with cotton wool for the audition. For actual filming, he wore a mouthpiece made by a dentist; this appliance is on display in the American Museum of the Moving Image in Queens, New York.

Anthony Perkins auditioned for the role of Sonny Corleone but it went to James Caan

Gianni Russo used his organized crime connections to secure the role of Carlo Rizzi, going so far as to get a camera crew to film his own audition and send it to the producers. However, Marlon Brando was initially against having Russo, who had never acted before, in the film; this made Russo furious and he went to threaten Brando. However, this reckless act proved to be a blessing in disguise: Brando thought Russo was acting and was convinced he would be good for the role.

Al Pacino, James Caan and Diane Keaton were all paid $35,000 for their work on the film.