Celebrity costumes? HELP?

I have a school dance coming up next week, and the dress code is to dress up as a celebrity. I have no idea who i am going to go as, and i want to go as someone who can be fairly distinguished as to who they are. Like some could be easy like Lady Gaga, Katy Perry, Justin Bieber etc... dead or alive celebs are both fine!! and male/female ! i really don't mind. PLEASEEEE HELP. thanks guys xoxx