I know what you are. What am I? You're the same thing, only ...
Dean: I know what you are.
Lucifer/Sam: What am I?
Dean: You're the same thing, only bigger. The same brand of cockroach I've been squashing my whole life--an ugly, evil, belly-to-the-ground, supernatural piece of crap. The only difference between them and you is the size of your ego.
Lucifer/Sam: I like you, Dean.