A clip from the movie “The Hangover" is titled as “What Happens In Vegas, Stays In Vegas" in which Sid Garner tells Alan that Remember, what happens in Vegas stays in Vegas. Except for herpes. That shit'll come back with you. This is the most comic and popular scene of a Las Vegas-set comedy centered around three groomsmen who lose their about-to-be-wed buddy during their drunken misadventures, then must retrace their steps in order to find him.