I don't think that's a costume. One of those kids is from Georgia and the other one was from Eastern Europe. IIRC, they were together for some sort of wrestling tournament. Pictures of them ran in major newspapers.
EDIT: After looking at the pic again (you can see some writing about the Big Mac sign on the window in other photos of this that I found) and doing some digging, it looks like it was taken over in Europe and the pic was actually an AP photo.
