In 1928, Walt Disney released one of his first films: Sleigh Bells. This 6-minute short featured Oswald the Lucky Rabbit, a prototype for Mickey Mouse. Embedded above is a short clip from it.
Although other Oswald films survived, Sleigh Bells vanished from film holdings. There were records of the film, but no surviving copies until a researcher found it in the archives of the British Film Institute. Disney has taken possession of this copy and is preserving and duplicating it.
-via Nag on the Lake