In the making of Toy Story 2, the animators and engineers used a lot of Linux and Unix systems. Those systems have a super-helpful command, RM*, that deletes everything in the system as fast as possible. Oops. And that’s why you always make a backup.
Watch the video below to see how they saved a year’s worth of work on Toy Story 2, and check out Quora for some more backstory from Oren Jacob. (Hat-tip: J. Walter Weatherman and Kottke. Video from the BluRay edition of Toy Story 2.)