Pacino was far from the first choice to play Michael Corleone:

Al Pacino’s portrayal of Michael Corleone is so definitive both in his career and in cinema history that it is hard to imagine anyone else in the role, but the young actor wasn’t the studio’s pick for the part. Paramount Pictures wanted established stars Robert Redford or Ryan O’Neal to portray Michael, and other big names including Warren Beatty, Dustin Hoffman, Jack Nicholson, and Rober DeNiro all expressed interest in the role. However, director Francis Ford Coppola stuck by Pacino, and the rest is history. 

A real mob enforcer played the role of Luca Brasi:

Former pro wrestler turned Colombo family bodyguard Lenny Montana played Luca Brasi in the film. During meetings with the Italian-American Civil Rights League, who were monitoring the portrayal of the mafia in the film, Coppola met Montana, who was working as a bodyguard for the Colombo crime family. The amateur actor was so nervous to act with Marlon Brando that he stuttered and looked visibly nervous in his scene, but Coppola liked the shot and it became an iconic scene for the humanisation of a supposedly merciless killer. 

The horse head was real:

A fake horse head was used in the rehearsals for the scene when the movie producer Jack Waltz wakes up to the bloody, severed head, but Coppola managed to replace it with the real thing for the actual take. This meant that actor John Marley’s visceral, panicked screams were in fact real, in surprise of bloody, enormous horse head in front of him. 

Brando used cue cards:

Marlon Brando received an Oscar for Best Actor for his role as patriarch Vito Corleone, and his performance remains an indelible part of the pop culture imagination forty-six years later. However, Brando refused to learn his lines completely, and he insisted on reading his lines during the take to improve spontaneity. He had the crew tape cards with his lines to lamps, bushes, and even actors to keep them out of the shot. 

The words ‘mafia’ and ‘mob’ are never mentioned in the movie:

The Italian-American Civil Rights League and pressure from the New York Mafia pushed Coppola to omit the words from the script, pulling the story closer to fiction even as it was based on a real culture. The Mafia continued to keep close tabs on the film, with members hanging around the set and appearing as extras in scenes. 

Watch the original cinematic trailer for The Godfather below: