wilhelm scream

Back in 1951, a voice actor recorded a scream for the film Distant Drums, for use in a scene where a cowboy gets his arm bitten off by an alligator.

Innocuous enough. However, it seems the sound engineers have been using this scream ever since, in a variety of bizarre places - from Aladdin and Toy Story to Star Wars and Transformers.

This video from YouTube is golden - it features clips from some of the films that have used the scream.