[Seeing the Yiddish Parrot made me think of Isaac Asimov; that was one of
his favorite jokes. In memoriam, here's another joke, this one
actually written by Asimov...]
John: Dave, you hear about my wife?
Dave: No, what?
John: She ran off with my best friend.
Dave: Sorry to hear ... hey, wait, I thought I was your best friend.
John: Not anymore.