It was a parody of a game.
Several random valve characters (and some from other franchises) rose up on a platform and danced against another group of people. It was kind of like a memorization game, one group would do ^ V > < w/e and the other group would do that and then they added another move. I don't know why I need to see this so bad, but I liked the author a lot. His videos were mostly valve-related I think.
