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Last night Britney Spears was presented with the Key to the City of Las Vegas by Clark County Commission Chairman Steve Sisolak, but that wasn't the only thing she had to celebrate -- the powers that be in Sin City officially made Wednesday November 5 "Britney Day"!

And it seems like Britney will be in Vegas for a while, as the pop princess has announced that 36 additional shows have been added to her "Piece of Me" residency at Planet Hollywood. After being honored by local officials and celebrating with fans, Brit Brit was treated to a performance by a handful of Las Vegas showgirls from Jubilee at Bally's, and at the event she ALSO announced her partnership with Zappos and the Nevada Childhood Cancer Foundation (NCCF)!

"I am so proud to join forces with the Nevada Childhood Cancer Foundation and support children and their families in need in my second home of Las Vegas, Nevada," Britney said in a statement. And we're guessing after this, she went to bed -- talk about a busy day!