Seven years ago, this happened in SPN: Lucifer: Castiel. I don't understand why you're fighting me, of all the angels. Castiel: You really have to ask? Lucifer: I rebelled, I was cast out. You rebelled, you were cast out. ... We're on the same side, like it or not, so why not just serve your own best interests? Which in this case just happen to be mine?
Last week, this happened in SPN: Castiel: Can you really beat her? Lucifer: I can. Castiel: Then yes.