My seven year old is really (REALLY) into Black Holes. He loves everything about them and can tell you pretty much all you've ever wanted (or not wanted) to know about them. He respects the theory of White Holes too, but agreed for his Halloween costume this year he would stick to what is a proven astronomical occurrence.
I am still trying to work out the logistics on his costume. I'm envisioning a wire frame, wrapped in fabric (space time fabric, if you will). How I'm going to keep it from impairing his vision and movement or falling off of him completely is still a mystery. I'm not a betting woman, but if I had to wager I would say it will require lots and lots and LOTS of duct tape.