Yes - it's the Supernatural cast and crew doing the Harlem shake, SPN style at a crossroads in a devil's trap!
So glorious in its dagginess! What we've gleaned, mainly from Guy Bee who 'directed' it, the whole thing was Jensen's idea! He showed Guy all the parody vids of it and said "we've got all that stuff!" they filmed it on 25/2, but only just got WB permission to post it.
I've collated fandom's guesses so far at who's who - let me know if you know any others. Osric apparently came in on his day off for the pleasure of rolling around in the dirt in a body bag! Seriously how can you know lvoe being part of this fandom?