Britney Spears, Demi Lovato Britney Spears, Demi Lovato

After months of speculation, Fox officially announced that pop superstar Britney Spears and teen sensation Demi Lovato will join The X Factor's judging panel when Season 2 premieres this fall. TV Guide Magazine spoke with Simon Cowell, L.A. Reid and Lovato just hours after they made their first appearance at Monday's Fox Upfront in New York City.

"Britney was a no brainer," Cowell said. "We'd spoken a few times, and I'd heard that she wanted to make one of these kinds of shows — but never thought she would agree to it. We got on so well on the phone, it went very smooth in the end." Spears was rumored to be in negotiations for a few months, finally settling on a deal worth around $15 million.

"Demi, I've been a big fan of for a long time and always had a gut feeling she'd be great on one of these shows," Cowell added. "Again, when we spoke we got on really well...and she's troubled!" The Disney star, who appeared on Sonny With a Chance and the Camp Rock series, entered rehab in 2010 for emotional issues, an eating disorder and self-injury. In 2011, she released her album Unbroken and the first single, "Skyscraper," recently went platinum.

"I'm just so honored to be here. I'm so stoked," Lovato said. "I think it's going to be a lot of fun, and I can't wait to argue with these two."

"Yes, she's very feisty," Cowell replied.

As the only original judge besides Cowell to return, Reid is enthusiastic about the changes and looks forward to the show's renewed energy. "I'm particularly excited to work with both of them," he said. "I think it's perfect. I think Simon is a complete genius to cast the both of them."

Auditions with the new judges begin next week in Austin, Texas. Cowell promises more changes are on the way, including the appointment of the show's new hosting duo.

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