Video store manager Natalie Martinez, who has been a "Big Brother" fan since the show's beginning, is only interested in one thing: winning.

The 24-year-old recent Arizona State University graduate from Gilbert, Ariz., said she doesn't plan on telling her competitors that she won a bronze medal for tae kwon do at the Junior Olympic Championships in 2002.

"They're not going to know," she said.

"I'm not telling anybody about my tae kwon do. I would be shooting myself in the foot to let people know I'm a competitive athletic person. I don't want people to know that.

"I want them to think I'm this sweet little girl who's not strong, not smart and won't win. I want them to see me as someone not to worry about."

This season, the California-themed "Big Brother" dwelling will go green with several eco-friendly touches including organic soap in the bathroom, energy-producing exercise bikes in the gym and composting bins in the backyard.

Executive producer Allison Grodner teased that one of the three bedrooms, a jungle-themed enclave, will feature a nasty surprise.

"It is a room that will test their resolve," Grodner said during a recent tour of the newest "Big Brother" house.

"I will go out on a limb and say that it is the worst room to sleep in any 'Big Brother.' After 11 seasons, that's saying a lot. This is a special treat for the houseguests. Each week, one group of houseguests will end up in this room."

At the start, the cast will be divided into teams. One clique will be joined by a mystery 13th houseguest when the show premieres Thursday.

Rumors have been swirling online that the 13th spot would go to a contestant who appeared in a previous season of "Big Brother." HTML code on the show's official Web site points to someone with the first name Brian.

The confirmed contestants of "Big Brother":

Braden Bacha, 28, model-actor from Santa Monica, Calif.

Kevin Campbell, 29, graphic designer from Chula Vista, Calif.

Laura Crosby, 21, bikini model from Atlanta.

Russell Kairouz, 24, mixed martial arts fighter from Walnut Creek, Calif.

Jordan Lloyd, 22, waitress from Matthews, N.C.

Natalie Martinez, 24, store manager from Gilbert, Ariz.

Michelle Noonan, 27, neuroscientist from Pasadena, Calif.

Jeff Schroeder, 31, advertising salesman from Norridge, Ill.