Celebs Celebrate Halloween 2011 Actress Katrina Bowden attends the Malibu Black Halloween party in New York on Oct. 27, 2011 dressed as a zombie fairy. Kim Kardashian dressed as Poison Ivy as she hosted Midori's Green Halloween at Lavo in midtown Manhattan on Oct. 29, 2011. Holly Madison parties at the 3rd Annual "Hollyween" at Studio 54 at MGM Grand Resort and Casino in Las Vegas, Nevada on Oct. 29, 2011. Gwen Stefani dressed as Cinderella for a Halloween costume party at Beverly Wilshire Hotel in Los Angeles, Calif. on Oct. 29, 2011. Mariah Carey and Nick Cannon, and twins Moroccan and Monroe Cannon pose in matching "The Incredibles" Halloween costumes. Bethenny Frankel was one of the many on hand at Heidi Klum's 12th Annual Halloween Party Presented By Tao Nightclub At The Venetian Resort and Casino in Las Vegas, Nevada on Oct. 29, 2011. Nicole "Snooki" Polizzi celebrates Halloween with a ...