Belphegor: Shouldn't we at least try and be friends? Sam and Dean, they seem to be coming around. I think I'm, uh, growing on them. You know, like a cancer.

Castiel: You are not growing on anyone. Sam and Dean are just using you. Don't mistake that for caring about you, because I can assure you they don't.

Belphegor: Wow. You learn that the hard way?