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Even the biggest reality TV fans know that those shows are staged, but now Kristin Cavallari is giving specifics about what was fake on "The Hills."

The former MTV star, who is pregnant with her second child, told Bethenny Frankel that she had "fake relationships, fake fights" while filming the series.

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"I knew exactly what I was getting into," Cavallari said. "I knew exactly the character they wanted me to be, so I said, 'I'm game. What do you want me to do?'"

For starters, she said, they asked her to stage a relationship with Brody Jenner, her real-life ex-boyfriend who was dating model Jayde Nicole at the time.

"They pretended like him and Jayde broke up and I was dating Brody, and then Jade and I got in a huge fight because she saw us out at the club, which wasn't real at all," she said. "They were together the entire time."

Now, Cavallari, who is married to NFL quarterback Jay Cutler, has bigger concerns. The 26-year-old said that she and Cutler will find out the gender of their baby on Christmas day.