She's one of the biggest pop music sensations of all-time, but even Britney Spears got booed while judging the new season of Simon Cowell’s “The X-Factor,” which returns to Fox Wednesday night.

“It was hard for me at first, and then you gradually get used to it. It’s hard because they all boo you,” Spears told FOX411’s Pop Tarts column. “You have got 5,000 people behind you and they actually love everyone. So if you say no, they go crazy.”

In fact, the notoriously harsh Cowell even claimed that Spears’ striking ability to turn away contestants made him look like “a softie.”

“I actually came over as a softie. I would say yes, and [Spears and Demi Lovato] are looking at me like these people are never going to be stars,” he remarked.

So what does it take for Spears to say yes?

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“The package. I want them to be able to perform, I want them to feel alive onstage, and of course the voice has to be amazing as well,” she said. “To combine all those three things is the ‘it’ factor for me… It’s a thrill and is so much fun when you actually see it, when you see someone come to life on the stage and deliver the way they are supposed to. It is just the best feeling.”

And although Spears has now happily settled into her judge's role, Cowell did have to step in with some early words of reassurance.

“I always know that on the first day, whoever we hire, within two or three hours there is going to be a ‘what the hell have I done?’ Everyone goes through it,” he said. “(Britney) is a good judge, and I had a feeling she was going to be a good judge, and the reason I say that is because nobody can survive at the top for a long period without really understanding music.”

“The X-Factor” Season Two debuts on FOX this Wednesday 8/7c.