The passing of Halloween can mean only one thing: Candy canes, Christmas trees, tinny versions of “Little Drummer Boy” on the drugstore P.A. system. The holiday season is here, and with it comes the annual delivery of sparkle and shine to dress departments throughout the land. This season stands to be even more sparkly and shiny than usual, inasmuch as the key look from now until New Year’s is flapper-inspired and as decadent as the roaring ‘20s themselves. The trend has its origin in last year’s Poiret exhibit at the Met’s Costume Institute, and got its legs at the Fall/Winter shows, with their unapologetic Poiret debt. Proenza channeled the master best – their opulent cocoon coats and cloche hats were pure Dorothy Parker and basically to-die-for – but it’s at Kate Moss’s for Topshop that you’ll find the pithiest expression of the Gatsby mood. Spotty until now, Moss’s line is finally living up to its notoriety with this Holiday collection. Think: Dropwaist dresses chandeliered with beads, lace boleros, reflective patent leather accessories, gold and silver lame. And, like Moss herself, think simple: At last month’s Fashion Rocks outing in London, Moss’s flapper look was stripped down; she’d modernized the aesthetic by simplifying it. Needless to say, she was a roaring success.