New York radio station Z100 announced over the weekend that pop superstar Lady Gaga has agreed to perform at its Jingle Ball at the Madison Square Garden on December 9th.  Gaga joins an already-star studded cast of performers at the annual event, which includes Pitbull, Kelly Clarkson, Demi Lovato, David Guetta and many more.  Guest hosts for the event, meanwhile, will include Kim and Khloe Kardashian and Lamar Odom.  Tickets, the station said, will go on sale November 1st at 4 PM to the radio station's ZVIP members, with tickets available to the general public the following day.