A few years ago, I saw actor Ned Beatty being interviewed by Bob Costas, and they began talking about Robert Duvall. Beatty is a great admirer of Duvall's, and mentioned that if you listen closely while watching "The Godfather", you'll notice the Tom Hagen character using different accents depending upon whom he is talking to. With "family", he uses one particular accent. When functioning in his capacity as a lawyer, he uses another. With others, another accent emerges. It's subtle, you assuredly won't notice it unless you're paying special attention, and Beatty noted that this is the mark of a truly great, dedicated actor. As an Irish-German kid growing up in a heavily Italian neighborhood, I always related to the Tom Hagen character, and always get a laugh when Jack Woltz gruffly refers to him as his "Kraut-Mick friend!" (I'm almost embarrassed to admit how many times I've seen "The Godfather"). They filmed a lot of it around NY's Little Italy not long after mobster Joe "Crazy Joe" Gallo was paroled from prison. Gallo, a colorful but deadly gangster, had made a lot of enemies over the years, and there were a lot of people gunning for him (he used to eat regularly at Luna's Restaurant on Mulberry Street, which remains one of my favorite Italian restaurants, although I haven't been there in a few years). Duvall was warned during filming to not walk around too openly in Little Italy, as there was a superficial physical resemblance between him and Gallo, and nobody wanted Duvall shot by mistake. As for Gallo, the people gunning for him finally caught up to him at Umberto's Clam House (just down the street from Luna's) in April 1972.

Tom Hagen, the non-Sicilian consigliere was well done by Duvall,  and his role really strengthened this movie.

Brilliant performance as the Corleone's consigliere and foster son, equally brilliant in the first pair of films, and I would argue that his absence from the third flick was a major contributing factor in that film's ordinariness.