Alec Baldwin as Vincent seems true and may have been his before he dropped out, part of a strange late-80s run of decisions.
Nicolas Cage, a family member, could have been good.
From internet lists, Tom Cruise, Matt Dillon and Val Kilmer are not believed; Charlie Sheen maybe; Vincent Spano makes sense; Billy Zane is listed; a Luke Perry audition is doubted; where they landed was right.
De Niro wanting to play Vincent, with Pacino aged up, seems true; Coppola did think about it.
Sinatra for Altobello is carried into the what-ifs alongside the names mentioned for Vincent.
The actor who played Willie Cicci (transcribed "Joe Spinelli") was supposed to work for Zasa but died before the movie, so the character was written out.
Paramount approached Sly Stallone, Scorsese, Cimino and Warren Beatty over the years; in the early 80s Stallone was to write and direct with John Travolta, and there is an internet rumor that Eisner took a run at the script.

Recasting Couch

Laura San Giacomo as Mary; William Hurt in George Hamilton's role

In the discussion (10)

Approx. transcript time · 01:08:54Read transcript

A replacement for Altobello would need an Italian-American actor of the era with Sinatra-like charisma; Paul Sorvino is unavailable because of Goodfellas.
Casting Wallach may echo the Lee Strasberg gamble, but it telegraphs the villain because he has played so many heavies.
Dennis Farina, Mickey Rourke and John Turturro were apparently in talks for Zasa.
David Caruso as Altobello and the Gilday actor playing every part are joked about.
Laura San Giacomo as Mary is restated as an amazing recast.
For George Hamilton's part the runners-up are Richard Gere, Harrison Ford and Paul Newman; Newman as Altobello is floated and welcomed as a good spitball, and Newman as Archbishop Gilday gets laughs.
The winner for Hamilton's part is William Hurt, called a no-brainer who looks like Duvall and could be Hagen's Harvard son as the new consigliere.
Recasting Hagen himself with Hurt is rejected as anti-recasting, and a Hagen son working for Michael is questioned given Michael's record.
Keaton's hair is the only other recast.
Brando as Altobello is rejected as too distracting, being much older and heavier, though The Freshman is liked.

Half-Assed Internet Research

A 1979 first draft built around Anthony and a CIA plot; Sofia Coppola appearing in all three films; 2,000 auditions for Anthony; a planned fourth film with Garcia and DiCaprio

In the discussion (9)

Approx. transcript time · 01:13:31Read transcript

The first draft was written in 1979 by Dean Reisner from a Puzo story, built around Anthony as a naval officer working for the CIA in a plot to assassinate a Central American dictator; it came in too hot for the studio.
Making Anthony an opera singer is liked by one host, while whether Michael lets him sing is called a stupid subplot and his restaurant song does not move another.
The restaurant song works because of the Apollonia flashbacks, the only time Michael was truly happy. — Bill Simmons
Sofia Coppola played the infant in the first film's baptism and an immigrant child in Part II, making her one of the only people in all three movies.
About 2,000 people tried out for Anthony; nobody remembers the actor's name.
The hosts relay that Andy Garcia once described a planned fourth film with him as Vincent and DiCaprio as young Sonny, mirroring Part II; it would now be exciting, though one view is that once Michael is dead the Godfather is dead.
Rocky Balboa and Creed are cited as ways sequels ignored weak entries; De Niro and DiCaprio as young Sonny and Vito would be worth seeing, perhaps with Vincent facing Gotti in the late 80s.
Coppola made only six more movies; 30 years have now passed, nearly twice the gap between the second and third films.
Another Godfather movie would be watched if set now with grandchildren and new characters, though remakes are rejected.

Nobody being horrified by the incest plot; Archbishop Gilday running the Vatican's finances; the hard-to-follow Vatican plot; the unresolved $600 million deal; no scene of Michael taking Kay to Apollonia's house

In the discussion (6)

Approx. transcript time · 01:19:35Read transcript

Why was nobody, Ebert included, more horrified by the incest plot?
What was the vetting process that put the nervy chain-smoking archbishop in charge of the Vatican's finances?
The Vatican storyline is so hard to follow that it needs a quiz on 40 characters and 19 subplots.
What happened to the $600 million Immobiliare deal after Mary dies, and did Michael end up running the Vatican Bank's finances?
The film should have had Michael take Kay to the house where he lived with Apollonia and come clean about the marriage; the idea is accepted as cool.
Apollonia is argued to be Michael's true love rather than Kay, while another host calls true love the 11th most interesting thing about the trilogy.

Probably Unanswerable Questions

How Vincent became the Don so fast; how much time passes between Part II and Part III; how old Mary is

In the discussion (4)

Approx. transcript time · 01:24:26Read transcript

How did Vincent go from a hotheaded leather jacket to Armani-wearing Don in two scenes?
The timeline is worked through: Fredo is killed in the early 60s, the third film starts in 1979, so roughly 15 or more years pass.
Mary's age is estimated from her line that she was 8 when Vincent was 15 and her appearance in Part II.
A made-up claim about Michael and Al Neri discussing the 1961 World Series tests whether Chris is paying attention, leading to a Mazeroski and Pirates exchange.