Minutes after posting the photo, the quartet attended an official presentation in New York.
Britney, who arrived in a white mini-dress but changed into a burgundy one for the official photos, said: "I'm so excited by this whole experience. It's so different from anything I've ever done."
Simon said of the...Baby One More Time singer – who found fame with the track aged 16: "Britney remains one of the biggest stars in the world, she's talented, fascinating - and I believe she knows exactly how to spot the x factor."
He was equally complimentary about 19-year-old Demi, first seen on Disney show Sonny With a Chance before she launched herself as a pop singer.
"Demi's had an amazing career in music, TV and film for someone her age. She's young, confident, and enthusiastic. I think it's really important that she speaks to our younger audience," he said.
Details of the judges salaries are not known, though Briney is rumoured to be pocketing $15 million a year for doing the show – making her one of the most highly-paid reality TV judges.
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It's a little princess!