Movie : The Playhouse (1921)

The opening scene, a dream sequence prior to the vaudeville routines which follow, is what makes this film famous.
In it Keaton plays everyone in a theatre simultaneously (through multiple exposures).
He is the band leader, all its members, the dancers on the stage and everyone in the audience.
Run time: 22 min
mpeg-650mbs

The_Playhouse.mpeg  

or
mp4

The_Playhouse_512kb.mp4 

thanks to ia
zenjoy