Simon Cowell is usually known as the "mean one" on whatever series he is seen. "American Idol" made him famous for his brutal critiques of hopeful stars, but now Cowell has made the claim that Britney Spears is "surprisingly quite mean" on his show, "The X Factor."

Spears "is a fascinating person because you just don't know anything about her," Cowell told reporters during a conference call. "She's very unpredictable. You never know what is going to happen. She has taken this very seriously and she's surprisingly quite mean."

Cowell is one of the creators of the series, as well as a judge of competitions. He has worked alongside Paula Abdul, Cheryl Cole, and L.A. Reid, but they left after only one season. Many speculated about who would become the replacement judges on the series. On May 14, it was announced that Britney Spears and Demi Lovato would fill the chairs.

It was a bold choice for Cowell, with Spears' tumultuous past and career history. And now it appears as though Spears is working to shed her "nice girl" image and follow in Cowell's footsteps.

"In the past, we've had judges that never say no," Cowell explained. "But she can't say no quick enough on the show. She's quite difficult to please. We have no control over [Spears and Lovato] whatsoever, and there are many, many times that we disagree."

"That's what's made it more interesting this year," he promised. "They are both unpredictable and have different and strong views."

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"The X Factor" is a phenomenon in the U.K., and it was created by Cowell, who made the decision to bring it to the United States. The show has caught on and provided a significant rival to the immensely popular "American Idol," on which Cowell began his judging career.

Watch Spears on "The X Factor" starting on Wed., Sept. 12 on Fox at 8:00 p.m. EST.