Meet the Punkin co-crafted w. @huertanix at NYC Resistor's Hackoween event last weekend (one pun too many!). One-size-fits-all Punk helmet with elliptical openings on the side (pumpkins are flexible). Carve it out well and your hair won't get soggy.
Check out David demoing at MakerBot's Halloween party (starts at 2:07)
Another headgear experiment of mine here.
Doubles as a lampshade