In 1951, a sound designer on a Gary Cooper western called Distant Drums needed to overdub a scream onto a scene in which a man is killed by an alligator. He brought a contract actor into his studio and rolled tape as the man did six brief, anguished screams in one take. These screams were then added to the Warner Brothers sound library, and over the next couple of decades they found their way into dozens of Warner Brothers films.
In the mid-'70s, a young sound designer named Ben Burtt gave these sounds a name: "the Wilhelm scream," after a character in one of the earliest films that utilized the sounds. A couple of years later, Burtt was hired to work on a film called Star Wars. As an homage, he overdubbed the scream onto a scene in that film. Then he overdubbed it onto a scene in The Empire Strikes Back. And Return of the Jedi. A fellow Lucasfilm sound designer began using the Wilhelm too, in Raiders of the Lost Ark and Indiana Jones and the Temple of Doom, among other movies. And thus a film-geek in-joke was born. In the last 30 years the Wilhelm has been used winkingly in dozens of movies and TV shows, from Reservoir Dogs and The X-Files to Aladdin and Return of the King.