How about, say, old yellow-eyes isn't a demon but a terminator? We all know there are red-eyed ones and blue-eyed ones; well, this is a different model, a yellow-eyed one.

Possibly the time travel thing was fucked up, it came back to kill Sam and/or Mary, but was interrupted. Because Sam is the boy king at the end of the world, rite? Just like John Connor.

Anywayz, the Colt is a spesh electrocution gun. In about 15 years Dean is going to go back in time and build it, piece by piece.