This is one of the strangest viral videos I’ve ever come across.
Called The Dogway Melody it was a short made in 1930 that recreates scenes from early musicals, such as The Broadway Melody. As you can see the cast are trained dogs with humans providing the voiceovers.
It was directed by Zion Myers and Jules White and is part of the MGM produced series of Dogville shorts.
> IMDb entry for The Dogway Melody
> More discussion on the MGM Dogville shorts at ToonZone