Getting "The Look"
Obviously, Brando didn't quite look like Don Corleone. He had to age himself and create an entirely different "face" just for his audition. Naturally, the film team loved his look.
Wide Mouth
For his audition, he stuffed his cheeks to give himself that defined jawline and droopy mouth. The film crew loved this look and had him recreate it for when it was time to film. Brando ended up meeting with a dental team so that they could design a custom mouthpiece for him in order to secure this vision.