Tonight, he makes his debut as one of the coaches on Spike's "Ultimate Fighter 5," one of the most popular cable shows on TV.

Showtime is 7 p.m. The Ultimate Fighter is a reality series that has been nominated twice for Emmys.

The show spends six weeks tracking 16 mixed martial artists as they live with and fight each other for a chance to win a six-figure UFC contract.

Each week, the coaches on the show pick two fighters to square off against each other, with loser going home in elimination fights. Then the coaches, save for last season's comeback-themed show, are featured on a pay-per-view card that will be held in Las Vegas in June.

The show's impact for a fighter can't be understated.

Season I coaches Randy Couture and Chuck Liddell became living legends outside of mixed martial arts world following the season-long build up and fight.

Matt Hughes, Rich Franklin, Ken Shamrock and Tito Ortiz have also seen their status grow after coaching on the show.

This year, the UFC is banking on the animosity between Penn and Iowa-based Jens Pulver to be the main sublot.

"I respect him — he's a world champion and I know he's dangerous," Penn, 28, told The Advertiser in an earlier interview about Pulver, 32. "But I just don't like him. That guy runs his mouth way too much"

Pulver's take on Penn: "He's not a rival anymore, he's a straight nemesis He's a great fighter. He's a legend in the sport. But I really want to knock him out."

Their history dates back to 2003 when Pulver beat Penn for the 155-pound UFC title.

Penn and Pulver, when not verbally sparring, will have eight fighters each to train.