In the stonkingly stupendous Boing Boing DIY Hallowe'en Costume thread, husband and wife Boing Boing readers and crafters Celeste and Jacob each wrote in to share this fun HOWTO.
My husband and I made some cross-culture Greek monsters this year: I am making a Kabuki Medusa costume, complete with home-made kimono and snake geisha wig, but I'm not quite done yet (tomorrow!).
However, my husband's Minotaur costume with a Venetian Carnival flavour was finished tonight and we're rather pleased. We made the bull mask from scratch, him modeling it out of cardboard and plaster and myself painting it. I made the toga as well. Here's the step-by-step process for the mask.