The "funny how" bit was heavily based on an incident Joe Pesci experienced as a young waiter when he complimented a mobster on his sense of humor. Needless to say, the man didn’t take it too well. Martin Scorsese heard the story during rehearsal and liked it so much that he let Pesci and Ray Liotta incorporate it by improvising their dialogue. The other actors in the scene weren’t given advanced notice because Scorsese wanted their genuine, unrehearsed reactions, and he shot it with only medium takes and no close-ups in order to capture their surprise.