My bf mentioned me dressing up as cheerleader do i have to do a cheer to?

So i have never been asked to dress up as something by a man. He mentioned he'd like me to dress up as a cheerleader in ping. I laughed! So he doesn't think it will happen but it will i just want to surprise him. But Do i have to do a cheer too or just outfit? Also what other ideas for dress up besides the typical ( ie: school girl, french maid, librarian)? Ant other ideas to have fun with?