Assuming you actually care about her, then be remotely nice. Nothing obscene/rude, illegal. LOL
Shaving cream trick is always fun.
Dress up like the Burger King King and blast a fog horn?
I've filled hundred of balloons and put them in a room while someone was sleeping. Hell, i could have detonated a nuke bomb and they still would have been sleeping.
Hiding under the bed with some evil toy and poking the mattress till they wake up, then scaring the crap out of them is always fun too. Exp. when you pass out UNDER a bed, then your friends go into YOUR room and decide you have sex on YOUR bed. In that case, they deserve GITMO/SAW movie type punishment.
Or if your cheap like me, you lay next to them and wisper in her ear "You wanna gimme $100, a BJ, a backrub and make me a ham sammich!"
On a side note, the last one has never worked completely. If it does work for you, see if she has a hot sister for me. LOL