This year me and my fiance dressed as Homemade Lego Minifig Men Costumes. The idea was simple enough and we had plenty of time to make the costumes. For the head we used a sono-tube (from Lowes) and papermache of a 12 inch bowl. She painted on the face and we used a little bit of screen where the mouth is to see out of it.
The body was the easiest, pretty self explanatory and the legs were a pain. If you are going use cardboard use clear tape because duct+carboard=no hold.