(Mandy, the waitress, seems to be interested in Cas...)
Dean Winchester (to Castiel): Dude, she is into you.
Mary Winchester: Dean...
Dean Winchester: No, this is good. We've been looking for teachable moments.
(Later):
Dean Winchester (about Cas): My shy but devastatingly handsome friend here was, just wondering, when do you get off?
Mandy: Whenever I can.
Dean Winchester: Hey-O!