"He may be a warlock," quips Bradley Cooper about his upcoming role on The WB's Sunday-night freshman drama "Jack & Bobby," "depending how the ratings go, and if we want to be more like 'Charmed.' You never know with TV."

The second WB show from "Everwood" creator Greg Berlanti (in partnership with Tommy Schlamme of "The West Wing") has been struggling in its 9 p.m. ET time slot (where it airs right after "Charmed"), despite generally good reviews (although it did just get a pickup for a full season of 22 episodes).

Christine Lahti ("Chicago Hope") stars as Grace McCallister, a politically liberal, single college professor in Missouri raising two teenage sons, Jack (Matt Long) and Bobby (Logan Lerman). What the audience knows but the McCallisters don't (through flash-forwards) is that Jack eventually dies prematurely, and Bobby goes on to become president.

Starting Sunday, Oct. 3, Cooper ("Alias," "I Want to Marry Ryan Banks") joins the cast as Tom Wexler Graham, a PhD. candidate working as Grace's new teaching assistant.

"He represents everything that she despises," Cooper says. "He's white, he's male, he's privileged. He comes from a really prestigious family, like his grandfather owned half of Rhode Island. There are lots of things she doesn't despise -- we just haven't seen them yet. She doesn't despise sexy, funny guys, you know what I'm saying?"

Tom gets the job because Grace's previous assistant -- a woman she hired even though Tom was more qualified -- has been fired for plagiarism.

"I'm the guy she never wanted to hire," Cooper says. "She also doesn't know who I am initially, because I didn't tell her. I tried to change my name, because I don't like growing up under this shadow."

Cooper hopes the interaction between Tom and Grace softens the audience's view of Grace, who usually comes across as strident and opinionated.

"They desperately need to show a different side of her," he says, "and that's what my character does. They couldn't get me on there fast enough. On TV, you have to persuade people to take time out of their lives every week to be with people that they want to be with. If you're not going to create people who you want to be around, the audience is not going to tune in.

"Her character is so strong -- and you're only seeing one side of her. You desperately need to show people that she's human. Once she's human, and once she's vulnerable, and once she's funny and likeable, then you're willing to put up with and even enjoy the other side of her."

While Grace has sparred with university president Peter Benedict (John Slattery), Cooper says the relationship between her and Tom takes a different tack.

"I'm extremely smart," he says. "I'm as quick as she is, so all of a sudden she has a counterpart. It's nice to see somebody go toe-to-toe with her and call her on her s***. The difference between Benedict and myself is, he's not intellectual. He's not an academic. He's a numbers-cruncher.

"I'm in her same world. We speak the same language -- and I'm white, male and privileged, so for her, it's very hard. Then they're building this sexual tension, and the great thing is, we actually have chemistry. The first three episodes just take place in her office on campus. Then she starts to mentor me through my thesis, so I go to her house. Then we partake in some extracurricular activities I can't mention.

"I was surprised when I read it. You'll see what I mean. I was surprised they'd allow that. How about that for a teaser?"

In a way, this represents wish fulfillment for Cooper. "I've always had a crush on Christine Lahti. I'm not kidding."

Having just come off playing a lead role in the upcoming feature comedy "Wedding Crashers" with Owen Wilson and Vince Vaughn, Cooper wasn't eager to drop back into a TV role, but he says, "The difference was Christine Lahti, because when I grew up, I thought she was sexy as hell."

There was another bonus to the role as well, in an episode airing Sunday, Oct. 10.

"Chad Everett plays my father in one episode," Cooper says. "He was literally like having a relic, in a great way. He's from a different time in moviemaking, in TV-making, in every way, down to his wardrobe, the way he spoke, his gait. It was just incredible. I love the guy."

This marks the second appearance this season on The WB for Everett, who had a brief role as the deceased patriarch in pilot for the Wednesday-night drama "The Mountain."

"Alias" fans no doubt wonder whether Cooper will again reprise his role as journalist-turned-government-witness Will Tippin. A regular when the show began, Tippin was written out of the ABC spy drama but returned for one episode last season.

"Maybe," Cooper says. "I talk to J.J. [series creator J.J. Abrams]. I know he definitely wants me to come back for two or three episodes. I hope [the producers on 'Jack & Bobby'] let me go do it."