one year for halloween i was a blue lego block.
here's how (although i doubt anyone cares to know, haha):
using a small, sturdy box, i cut away a curved portion (think half circle shape) so that the box could fit on top of my head. this also allowed my face to show. i painted the box blue, then let it dry. next i cut six equal pieces from an empty paper towel's cardboard roll, and painted them blue as well. once dry, i glued them to the top of the box.
i also painted my face blue and wore all blue clothing (jeans and a blue turtleneck). lame, but i was a poor college student and i wanted to be something that i hadn't been before. hee.
I hope you don't mind, I am totally going to do that this year!