Z100 Jingle Ball '08

Singer Katy Perry performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Rihanna performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Leona Lewis performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Actress and singer Ashley Tisdale addresses the crowd during the Z100 Jingle Ball in New York on December 12, 2008. (Reuters/Lucas Jackson)

Singers Rihanna and Chris Brown perform at the Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Chris Brown performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Paramore singer Hayley Williams performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Katy Perry performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Jesse McCartney performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Brandy performs at Z100 Jingle Ball 2008 at Madison Square Garden on December 12, 2008 in New York. (AP Photo/Evan Agostini)

Singer Leona Lewis poses in the press room at the Z100 Jingle Ball concert at Madison Square Garden in New York on December 12, 2008. (AP Photo/Peter Kramer)

Singer Rihanna poses in the press room at the Z100 Jingle Ball concert at Madison Square Garden in New York on December 12, 2008. (AP Photo/Peter Kramer)

Singer Lady GaGa poses in the press room at the Z100 Jingle Ball concert at Madison Square Garden in New York on December 12, 2008. (AP Photo/Peter Kramer)

Singer Rihanna poses in the press room at the Z100 Jingle Ball concert at Madison Square Garden in New York on December 12, 2008. (AP Photo/Peter Kramer)

Singer Katy Perry poses in the press room at the Z100 Jingle Ball concert at Madison Square Garden in New York on December 12, 2008. (AP Photo/Peter Kramer)