One of Caan’s earlier roles was in the film ‘El Dorado’ directed by Howard Hawks (pretty much a remake of ‘Rio Bravo’). According to Hawks, Caan wanted his character to be serious and dangerous, which wasn’t what Hawks had in mind. Hawks said he didn’t have to tell Caan to lighten up because the more serious Caan tried to act, the funnier it got. Caan had plenty of dark, dangerouse roles later on (see ‘Thief’, a sadly overlooked film) and he was great in a lot of those roles.
Caan got the nickname ‘Jewish Cowboy’ from his ‘El Dorado’ role.