Two thoughts I had earlier on; the first may have already been done.
Here they are:
1) A t-shirt for pregnant women (elasticated around the waist) that says “Who’s The Daddy?”. Maybe it’d only really work in America as it’s not really an everyday British phrase…
2) An advert for Norwich Union Direct featuring a naked woman (or man, I suppose, but woman preferred) sat at a computer ordering insurance online. The slogan being something along the lines of “Order your insurance in the NUD”.
Ha ha, I am funny.