Best of Britney Spears: See Singer From 'Baby One More Time' to 'Femme Fatale'

Britney Spears celebrated her 27th birthday in December 2008 by performing at the Big Apple Circus tent in New York City on "Good Morning America." Britney kicked off her comeback tour, "The Circus Starring Britney Spears," three months later at the New Orleans Arena on March 3, 2009, her first arena concert since 2004. (Ida Mae Astute/ABC)