How far should I take it?

A guy friend of mine and I were joking around about halloween and I told him I could make him look like a pable girl. He said he didn't think so. Long story short, we bet a whopping 500 dollars that I couldn't do it. We agreed to split all cost involved. I really could stand to get an additional 500 but geez, where should I start. Any suggestions would be greatly appreciated. I am going to need a really good idea for an outfit for him to wear too. He agreed to let me do anything to him as long as it was not perminant.