When Francis Ford Coppola called up Bob Hoskins to offer him a part, the actor didn't believe it was really him. Coppola introduced himself, to which Hoskins replied, "Yeah, and this is Henry the fucking Eighth", and hung up.
At one point relations were so strained between director Francis Ford Coppola and producer Robert Evans that Coppola had Evans banned from the set.
Laurence Fishburne's character was based on real-life Harlem gangster Ellsworth "Bumpy" Johnson. Thirteen years later, Fishburne played Bumpy in Les seigneurs de Harlem (1997).
Allegedly, the reconciliation scene between Owney Madden and Frenchy was written by Fred Gwynne. Francis Ford Coppola considered removing the scene during editing but was convinced by co-screenwriter William Kennedy to leave it in.