Britney Spears' "Circus" Comes to Town

Britney Spears celebrated her birthday with a pair of performances on "GMA."

PHOTOS: Britney Spears' 'Circus' Comes to Town

Britney Spears
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Celebrities John Travolta, Reese Witherspoon, Nicollette Sheridan and Terri Hatcher taped birthday greetings for Spears' birthday that aired on "Good Morning America" during her performance. People's Sexiest Man Hugh Jackman serenaded the pop princess with his version of "Happy Birthday." (Ida Mae Astute/ABC)
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