Bob Hoskins was Originally Signed to Play Al Capone
Robert DeNiro was pitched the Capone part early on, but said no.
So the producers signed British cockney actor Bob Hoskins -- based on his work in The Long Good Friday(1980) and, just recently, his Oscar nommed work in Mona Lisa(1986.) This was one year before Hoskins' biggest role (in Who Framed Roger Rabbit, where he got a role turned down by Harrison Ford!)
Hoskins was good to go but the producers took one more try at DeNiro...and got him. Hoskins was paid off in full, saying something like "Anytime you want to pay me my full price NOT to do a movie...you know where to find me!"
If Hoskins had played Capone, it would have looked like more of a supporting role...though his Oscar nom for Mona Lisa made him a bit of a star.
With DeNiro in the role, suddenly it took on more "expectation." This was the man from Godfather II (Oscar, supporting) and Raging Bull(Oscar, Best Actor.) This was a "prestige movie star."
Two years later, something similar happened in casting the Joker for Batman. Prestige superstar Jack Nicholson was pitched the Joker, but kept stalling(he never said no.) So Robin Williams was mentioned in the press as the Joker instead. Jack then said yes -- to big bucks and percentages of things like toys.
However, unlike as with Bob Hoskins as Capone, Robin Williams was neither signed nor paid off for playing the Joker.