Martin Scorsese is arguably the greatest living American film director, and since the very beginning of his decades-spanning career, he's made a habit of appearing in his films in small cameo roles.

No doubt taking his cue from filmmakers like Alfred Hitchcock, who was never shy of a cameo, his onscreen roles have been legion. Sometimes they're a fully realized character, such as his chilling turn as a cab passenger in Taxi Driver. Others he's more content with a blink-and-you'll-miss-it walk on role, or even a voiceover.