Fictional inspiration: Clint Eastwood
Real world inspiration: Frank Morris
Claude was Rockstar's first modern, open world protagonist. Even though he was the strong, silent type, the similarities between Claude and Eastwood are undeniable. Not old, Gran Torino/mildly senile Clint Eastwood either. Young, 'beat your head in with my bare hands' Eastwood.
Frank Morris, played by Eastwood in 1979's Escape From Alcatraz, was one of the only men to ever escape from Alcatraz. Eastwood played Alcatraz's most famous prisoner and it's easy to see how all three of these lantern-jawed men influenced one another.