Singing sensations The Jonas Brothers stunned fans during a recent New York concert when an unexpected guest took the mic - Britney Spears' former bodyguard.

The pop trio stormed the stage at Bryant Park to perform a free concert for an estimated 10,000 fans on breakfast show Good Morning America on Friday.

And Spears' former protector, known as Big Rob, was keen to join Kevin, 20, Joe, 18, and Nick, 15, on stage.

The burly bodyguard - who has been hired by the band to keep their legions of female fans at bay - collaborated with the boys on their hit single Burnin' Up.

Rob rapped onstage to the song during the record-breaking performance - which entertained the largest crowd the morning show has hosted to date.