I'd just start making things up to mess with them. "When are you due?" - "In four months. I'm having sextuplets." "Is it a boy or a girl?" - "Both! I'm having a hermaphrodite." "Wow are you sure there aren't two in there?" - "Yeah, there are, but I'm getting rid of one. Want it? Five bucks or best offer."
6/7/11 at 7:31am