Goodfellas (1990) - The “you think I”m funny, how am I funny?” scene was based on a story Joe Pesci told director Martin Scorsese. As a young man Pesci was working as a waiter and told a mobster at one of his tables that he was “funny”, and the mobster became furious. Scorsese let Pesci and Liotta improv the scene and didn’t tell the other actors, hence the geniune reactions.