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HEY MR. DJ!
Also at the 1 OAK Las Vegas blowout: Kanye West, who got the party started by spinning tunes under the pseudonym YeezyWorldPeace.
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Pitbull and Justin Bieber buddy up in N.Y.C.'s Times Square, where each appeared on New Year's Rockin' Eve. Pitbull performed his hits "I Know You Want Me" and "Give Me Everything," while the Bieb rang in the new year with something old: the Beatles classic "Let It Be."
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Vowing to and enjoy life following her recent double mastectomy, Giuliana Rancic cuddles up with husband Bill at the NIVEA Kiss Stage in New York's Times Square.
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Also at the NIVEA Kiss Stage in N.Y.C., Cee Lo Green wows the crowd with his take on John Lennon's "Imagine" for NBC's New Year's Eve with Carson Daly special.
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OUT OF THIS WORLD
In Los Angeles, a very Jetsons-esque Nicki Minaj looks ready for the future – which will likely include an appearance at the Feb. 12 Grammys – while performing "Super Bass" on Dick Clark's New Year's Rockin' Eve.
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Check out that footwork! Dancing with the Stars pro Karina Smirnoff has a heel of a time bowling with a bottle at Joonbug's End of the Year Bash in N.Y.C.
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ICING ON THE CAKE
Singer Bruno Mars caps off a blockbuster year – which included winning a Grammy, a Billboard Music Award and an American Music Award – with a sweet celebration at Las Vegas's The Bank Nightclub at the Bellagio.
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Shameless star Emmy Rossum turns up the heat in a strapless red dress during an appearance on NBC's New Year's Eve with Carson Daly in N.Y.C.
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HOST WITH THE MOST
A dashing Sean greets his guests, which include actress Vivica A. Fox (pictured), Gayle King and Star Jones, at the CIROC: The New Year 2012 bash in Miami, held at a private estate.
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Someone's feeling frisky! Brandy gives a peck to reported new beau Ryan Press at The Cosmopolitan of Las Vegas Celebrates New Year's Eve party, where music legend Stevie Wonder was the star attraction.
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After showing off her ice-skating skills, Holly Madison flaunts her famed figure while welcoming 2012 at the Chateau Nightclub amp Gardens in Las Vegas.
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Kate Winslet Takes a Stand on Bullying and Opens Up About Being Fat-Shamed: ‘They Called Me Blubber’
Reese Witherspoon’s Daughter Wishes Her Mom a Happy Birthday: You’re ‘One of My Best Friends’
From The Hills to The Windy City: Kristin Cavallari and Jay Cutler's Love Story
Ryan Gosling Explains Why He Got the Giggles During Oscar Flub and How it Feels to Be a Living Meme
Marcia Gay Harden Opens Up About Her Mother's Battle with Alzheimer's and Facing Its 'Scariest First Moments'