The invitation for The Art Deco Glitter Ball, a.k.a. the Marc Jacobs company holiday party at the Rainbow Room this week, asked guests to “Think Glitter:” “Think 1920’s Hollywood Movie Musicals!” “Think 1920’s Hollywood Glamour!” “Think 1920’s Busby Berkeley!” and sure enough, there were enough dancing girls to rival any Ziegfeld Follies. But this is the end of 2003, and so many of those dancing girls were actually men, who shared the rotating dance floor with dwarves, samurai, go-go boys, a couple dressed as the New York City skyline, Deborah Harry and the Pulitzer Prize-winning author, Michael Cunningham. As Anna Sui, Roman and Sofia Coppola and a Liberace-clad Robert Duffy judged costumes in categories like “Most Confused About Costume Concept,” Marc Jacobs created merry amusement as he bounced around in a chunky polar bear getup. “I bought it on the Internet for $600,” said a sweating Jacobs, espousing a carpe diem philosophy. “But I don’t think this is the kind of outfit you can wear twice.”