Willow Smith, B.o.B, and Bruno Mars Rock Z100’s Jingle Ball

Willow and Jaden Smith were the coolest kids at Madison Square Garden for Z100’s Jingle Ball 2010 on Friday (Dec 10). The superstar siblings took part in the annual holiday concert, where Justin Bieber, Sean Kingston, Katy Perry, B.o.B, Bruno Mars, and more hit the stage. Backstage, the Biebs cozied up with Kim Kardashian, Flo Rida showed up with girlfriend Eva Marcille, and B.o.B and Hayley Williams reunited.

“I’ve been looking forward to this show. I’ve never even seen Madison Square Garden. This is incredible,” said seven-time Grammy nominee Bruno Mars, who played the Garden for the first time in his career.

Check out more pics from the pop fest below.