Costume?!?

I generally don't go out. Call me boring, call me a homebody, I rarely go out at night...let alone with friends...to bars. Well, I got talked into going to a Halloween party at some bar with a bunch of co-workers this coming Saturday night. Now I have to figure out a costume! Nothing I really have at home fits. I thought I had a rat face, but I can't find it. I'm kind of thinking Wood Nymph, or female Bacchus, or, oh I don't know. And I need to find something quick-I can't leave it til I'm off work either, since that's Friday and this thing is Saturday. Yikes. I may have to go to Goodwill. Hopefully, something will pop out at me.