Kristin Cavallari Turns 'Hills' Upside Down In Teaser Trailer

Video shows Kristin dating Justin Bobby, while Spencer and Heidi talk babies.

Kristin Cavallari made a lot of promises that she'd be spicing things up when she joined "The Hills." And judging by a new teaser out for season five of the show, which premieres on September 29, she was telling the truth.

The clip confirms the rumor that Cavallari and Justin Bobby are starting up a romance, and it looks like Audrina Patridge isn't the only one who has a problem with her new co-star's ways.

"Lauren basically told us she's a man eater. She's a boyfriend stealer," Audrina shares about the new girl. Later on in the trailer, she says, "These are peoples' lives that she's messing with. People do have hearts and feelings."

Stephanie Pratt seems especially apprehensive about Cavallari. "She's like a disease you can't get rid of," she says. "She's the girl who's going to stab us all in the back, and she doesn't care. ... How can one person turn all of our lives upside down?"

Meanwhile, things get serious for Holly Montag, who is confronted about her drinking by her sister, Heidi Montag, and brother-in-law, Spencer Pratt, who would like to see Holly get help. "I think Holly might need to go to rehab," Heidi says. "I want to help [her] however we can."

And, as Stephanie hinted to MTV News earlier this week, Spencer reacts uncomfortably to Heidi's talk of wanting to start a family. He confides to his sister, "If you hear her talk about a baby, just tell her, 'Yo, Spencer's not having a baby for 100 years.' "