Britney's Boys On-Hand for Her Birthday Show!

Britney Spears couldn't have gotten a better start to her birthday, as the pop superstar celebrated her 27th with an impressive performance on Tuesday's Good Morning America. And to make it even more special, she had her two young sons cheering her on from the audience!

Three-year-old Sean Preston and Jayden James, 2, were seated with Brit's mom Lynne Spears in the second row of the Big Apple Circus in NYC to catch the singer's first live U.S. TV performance since her lazy and distracted run-through of "Gimme More" at the 2007 MTV Video Music Awards, the renewed and improved singer showed that she's still got the dance moves — and ripped abs! — that made her a sensation a decade ago.

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Dressed as the world's sexiest ringmaster, Brit entertained the screaming crowd of hundreds of fans, first with the title track off her new album, Circus, which was released today, and then later in the morning with her current hit, "Womanizer."

"She was so amazing!" One audience member told OK! after the show. "It's like that bad period earlier this year never happened. She's a completely different woman now!"

Celebrities from Reese Witherspoon to Taylor Swift to Nicollette Sheridan offered their birthday wishes to Britney via videotape. One clip, featuring Australia hunk Hugh Jackman singing "Happy Birthday to You," had Brit blushing. "Ohmygawd! That's awesome," she exclaimed.

The folks at GMA rolled out a mammoth, circus-themed cake to celebrate Britney's birthday, which was then fed to the audience.

Because there's nothing better for you than cake at 9am.