An ending that can be put onto the ends of stories and plans. A convenient phrase to use when your story or plan sounded really dumb. It usually doesn't make much sense.

From the days of newspaper TV Guides that would write two sentence synopses (loglines) of a television show. Sometimes these summaries wouldn't sound comedic on the surface, so "hilarity ensues" was used to ensure the audience understood it was a premise for a comedy.

Something funny is upcoming due to a build-up of circumstantial events, or a comedy of errors.

Sometimes involves rape.