What if Castiel had taken a different vessel?

“You’re Captain America!” I said, because he was. “Uh, hulloooo, standing right here,” Tony told me. He was using his obnoxious voice. “I know you’re there,” I said. “But Captain America! You didn’t tell me Captain America was going to be here!” A sequel to 'A Connection Is a Thing Which Requires Maintenance.'

Apparently Supernatural was real, which was presumably why Gabriel was bleeding out onto Richard’s floor. (In which the actors of Supernatural find that reality is stranger and more disturbing than they previously believed, even counting Misha, and an injured archangel discovers that his universe is the subject of a TV show.)