A lot of the film’s ad-libs come from James Caan, who played Sonny. During his fight against Carlo Rizzo, he improvised slamming the garbage can down on Carlos (it’s kind of easy to tell that he missed on purpose if you’re watching for it) and he also threw in saying “bada-bing” after hearing it from real-life mobster Carmine Persico.
He also improvised the move that establishes his character, where he threw an FBI photographer to the ground, and then tossed him a bundle of bills for breaking his camera.
Into the Thousands
"The Godfather" had an incredible amount of extras signed on to help, and there are few scenes that reach a monumental number. For instance, during the scene where Sonny brutalizes Carlo used over seven hundred extras while filming it.
The wedding scene tops even that, using more than seven-hundred and fifty. The number of extras gives the film a huge, real effect, and if you've ever been part of an Italian wedding, you'll find it runs pretty close to real life. Some of the guests don't even know the bride or groom!
Packing on the Pounds
Marlon Brando was a pretty big guy during the filming of "The Godfather". Even so, he decided to pull a few jokes on some of the other actors. When Don Corleone has to be carried up to his bedroom coming home from the hospital, the hectic scene is full of people trying to get out of the way and others trying to carry him up a set of stairs.
Marlon Brando decided he needed more weight in his bed, and packed it full of additional weights, just to give the actors who had to carry him a harder time.
On the Fly
Brando flexed his improvisational muscle during this epic film. His most famous addition to a scene was when Vito Corleone slaps Johnny Fontane, a singer, in the face. Actor Al Martino's shocked reaction was entirely real – it's not like he was expecting to get slapped in the face by the almighty Marlon Brando.
James Caan said that “Martino didn't know whether to laugh or cry.” Brando didn't miss a beat in the scene, continuing on with his rock-solid performance despite Johnny Fontane going wet in the eyes.
A New Way to Film
"The Godfather" has it all. Stellar performances, a grand musical score, and a brand new way of filming thanks to famed cinematographer Gordon Willis. He wanted the film to be all about the people and their points of view. Thus, he did something unique at the time, which was to make each shot in the movie from a hypothetical point of view of a character.
Though he didn't use the locations where real characters would be standing, he set up the cameras in specific places – and even at specific heights – so that they could be an onlooker.