Recalling our "Knock, knock" jokes of a while back.
I was trying to come up with one
"Knock, knock."
"Who's there."
"Barack."
And that's where it falls apart. If someone told me "Barack" was making a speech, or visiting Ireland, or whatever, I'd know instantly who it had to be. The only line I could come up with involved a frog, and that's not only not funny but obvious. I have nothing against cheap shots and rarely pass one up, but that one is a bit too weak.
Someone out there is more clever than I, I know.
Arf