If you blink you might miss them, and that would be a shame, because some of the funniest, coolest, most clever moments at the movies come when a director or producer throws a brief turn by a big star, without warning, into their film. Alfred Hitchcock, who had a nod-and-wink walk-on in every single one of his own films (including Lifeboat, which took place entirely in a tiny dinghy), is the patron saint of the cameo. Here are twenty one-scene wonders that might've amuse even Hitch.