I seriously think that God should be played as Morgan Freeman in Supernatural (if God is gonna 'be' in Supernatural)
God: Hello Sam, hello Dean, I am God
Dean: Oh, it's Morgan Freeman, *turns to Sam* look sam it's Morgan Freeman
Sam: Err, sorry I don't understand, Morgan Freeman... is God...?
God: It would be too overwhelming for your mortal eyes to perceive my true form... And I did quite enjoy that movie
Sam: So you're not Morgan Freeman
Dean: Who knew. I guess God has a sense of humor after all
God: *chuckles* What's even more funny is that face I gave you
Dean: Alright you sonuva-
Sam: Dean, DEAN. It's God.