Mario Puzzo nunca había escrito un guion antes de El Padrino. En una entrevista de 2019 relató que:

Después de haber ganado dos premios de la Academia, ya sabes, por los dos primeros “Padrinos”, salí y compré un libro sobre escritura de guiones porque pensé que sería mejor aprender. Ya sabes, de qué se trata aquello, porque fue algo que me salió de la cabeza. Y luego en el primer capítulo el libro decía, “estudia El Padrino I. Es el modelo de un guion”.

Vota!

Fuentes

TERRY GROSS. "A Look Back At 'The Godfather,' With Mario Puzo And Francis Ford Coppola". National Public Radio, 8 de marzo de 2019 https://www.npr.org/2019/03/08/701492922/a-look-back-at-the-godfather-with-mario-puzo-and-francis-ford-coppolaPUZO: Yeah, I mean, it was a cinch because it was the first time I'd ever written a screenplay, so I didn't know what I was doing. You know, it's - and it came out right. And the story I tell is that after I had won two Academy Awards, you know, for the first two "Godfathers," I went out and bought a book on screenwriting because I figured I'd better learn...GROSS: (Laughter).PUZO: ...You know, what it's about because it was sort of off the top of my head. And then the first chapter - the book said, study "Godfather I." It's the model of a screenplay. So I was stuck with the book.