How to make an elmo costume for pre teens?? 10 points for best answer??!!?

Me and 2 of my friends are going to be Elmo, Cookie Monster, and Big Bird for halloween. (My friend knows what she is going to do for her Big Bird costume, but me and my other friend don't know what to do about cookie monster and elmo) We are 12 years old. We want something thats not babyish, and doesn't involve a lot of sewing. Thanks!!!!! Please help!!!!!