Marlon Brando has plenty of eccentricities. One of them is he hates memorizing lines and required cue cards to be in sight at all times so he could get his lines right.
These cards were often hidden behind props and sometimes were even sewn into the clothing worn by Brando’s castmates. The reason Brando didn’t like to memorize lines is that he thought it ran counter to his method of acting. He wanted an off-the-cuff feeling for this powerful character, and a rehearsed feeling wouldn’t give the character the savoir-faire and easy power Don Vito should have.
Lots of Acting Options
Since the movie had lots and lots of roles, the cast was huge, and some incredibly famous and surprising names were considered. Robert Redford was considered for Michael Corleone, as well as Jack Nicholson, Dustin Hoffman, and Tommy Lee Jones.
Anthony Perkins and Burt Reynolds both auditioned for Sonny, and Steve McQueen, Paul Newman, and even Elvis Presley auditioned for Tom Hagen... but Presley was way more interested in playing Vito Corleone. No shade on Elvis, but we're kind of glad they went with Brando. Of all things, Sylvester Stallone auditioned for both Paulie and Carlo.
Method Acting Madness
At one point in "The Godfather", a corrupt police officer punches Michael Corleone and breaks his jaw, which leads Michael to kill the cop along with a few others. It's a critical step on his path to leading the Corleone crime family, but there's an interesting detail.
After Michael's jaw breaks, he gets it wired shut to heal. Al Pacino acts superbly during these scenes, helped mostly by the fact that he got his jaw wired shut in real life, too. Pacino is an actor dedicated to his craft, but this takes preparing for a role to a whole new level.
The Man and the Moon
It may come as a surprise when you find out that the actors spent a lot of time mooning each other. This was just one of the dozens of pranks and gags pulled in order to break up the tension of the movie, and it became the go-to gag.
Actors and crew got used to peeking around a door and checking for a bare bottom. Who was the best at this juvenile act? Brando, who thanks to his heroic efforts furthering the craft was nicknamed “Moon Champion” – he even got an honorary leather belt for his prank efforts.
Back on the Horse
Animal Rights groups complained about it. Cast and crew complained about it. Nevertheless, the legendary scene with the horse head remains one of the top-of-the-line movie scenes for fans and foes alike.
It's practically synonymous with the film, and it's the easiest way to invoke the spirit of the film. Yet the scene almost didn't make it into the finished product. Among the people who didn't like the scene at first was Coppola, who thought the book's presentation of the scene wasn't very good. In the end, he found it too good to leave it out.