"The upcoming meta-ep that takes the Winchester brothers into an alternate universe where they are (smoking hot) actors named Jared Padalecki and Jensen Ackles will also feature some other characters with names you might recognize — “Sera Gamble,” “Eric Kripke,” and “Bob Singer.” But don’t look for the real-life executive producers to appear as themselves; they will be played by actors. (Collective boo.) I also hear Castiel/Misha Collins will appear, but sadly, Jim Beaver will not."
Source: InsideTV