1. As a Trick The tradition of masked mischief in Venice began in the 11th century as part of the getup guaranteeing anonymity to boys, whose hobby it was to hurl eggs at young noblewomen. In and out of favor since then, Venetian masks were used to obscure the identity of those testifying in court or to enhance one's outfit for a night on the town. In the 17th century, they were ruled decadent and relegated to Carnevale. Masks disappeared when Napoléon gave Venice to Austria-only to return in the mid-20th century with commedia dell'arte theater. Today, souvenirs like this gold-painted, triple-faced fright are sold all over Venice.
2. As a Tribal Tradition It's the men who spend all day putting on their faces in the Huli tribe of Papua New Guinea. The vibrant reds, whites, and yellows-meant to mimic the colors of the bird of paradise, revered as a tribal ancestor-are achieved with a mix of ocher and mud. The men also grow their hair long, then chop it off to use in headdresses. Unlike the bird they emulate, they aren't preening for courtship. The wigmen, as they're known, pay for their wives in pigs and save the dress-up for a ritual dance celebrating clan pride.
3. As a Remembrance Morbid, gorgeous, or haunting, death masks were first created in ancient Egypt and remained popular as homages to public figures in 19th-century Europe. The one below captures the Romantic poet John Keats and was made from a clay impression taken after his 1821 death, at the age of 25. (The clay imprint was used as a model for the plaster mask.) For the poor and ailing poet, death was a common theme: My spirit is too weak-mortality/Weighs heavily on me like unwilling sleep. Today, his face, like his verse, lives on in the newly reopened Keats House in London.
4. As a Celebrity Replica Last Halloween, the top-selling mask was candidate Barack Obama. This year, retailers predict a major spike in Michael Jackson look-alikes. In fact, Ogawa Rubber in Japan started cranking out King of Pop likenesses just days after the singer's death. Also expected to fly off the shelves: Transformers and Star Trek rubber pull-ons. Jason and Freddy, from Friday the 13th and A Nightmare on Elm Street, will also get plenty of face time, predicts mask retailer Greg Banta. But for trick-or-treating, at least, good still wins out over evil: When it comes to costumes, year after year, princesses are still the bestsellers.