The Wilhelm Scream

There was a famous movie scream recorded way back when (earliest known use in "Distant Drums" - 1951) which made its way into stock sound f/x libraries and has become something of a Hollywood gag. It has been reused in almost every Star Wars film, Indiana Jones film, even in Disney cartoons. It supposedly showed up in the new Indiana Jones film, too, when Indy and Mutt were sliding under those tables in the library on the motorcycle -- a startled student shrieked it out. After you hear it once, you'll hear it everywhere.

LINK - a more detailed history of it over at DamnInteresting.com.
and
LINK - a hysterical compilation of Wilhelm screams from many of your favorite movies, over on YouTube.

So, if you're watching a movie or cartoon and some of the laughs or screams or miscellaneous sounds seem hauntingly familiar, don't be surprised if you really have heard them all before.