The worst(?) one I ever saw was a non-pregnant woman, went as a pregnant trailer trash or hill billy or white trash or whatever. She had a T-shirt (stuffed with a pillow) that said, "Drinking for 2". Terrible I know.
Anyhow 9 months is cutting it close. Here is hoping you don't go too early and have yet another halloween baby. (there seems to be a fair share on the forum).