MTV'S DUFF RECALLS THE TIME LAST summer that she forgot to pay her cable bill and her service was shut off. "I was calling to have them turn it back on," says the effervescent prime-time VJ, "and they're like, 'What's your name?' I'm like, 'Karen Duffy.' They're like, 'Oh, Miss Cable Star. Can't afford to pay her bill!' I held to beg them to turn it back on."

Not that she missed cable all that much. When she signed on with MTV 17 months ago, Duff, 31, didn't even have it—and that worked to her advantage. "I didn't see what I was doing," she says, "so it didn't inhibit me."

Since then, Duff's break-out personality has attracted enough industry-wide attention to take her out of MTV's iconoclastic corner and into the showbiz mainstream. In addition to her VJ duties—which include covering spring break this week in Daytona Beach—Duff is making a sitcom pilot for Fox and appears in Arnold Schwarzenegger's upcoming summer release, The Last Action Hero.

All this career rockin' and rollin' is a pleasant shock to Duff. The second of four kids in a close-knit Irish Catholic family, Karen Duffy grew up in a string of New Jersey towns. "I love the name Karen," says her homemaker mother, Carol. "But in third grade she just started calling herself Duff."

After majoring in recreational therapy at the University of Colorado, Duff eventually put her degree to work at a New York City nursing home, where she still volunteers two days a week. "I find that working with others [makes you] stronger and richer," she says. Duff discovered conventional wealth four years ago after a photographer suggested she model. On a lark she signed with an agent and went after movie parts. "I'm more confident with my mouth open," she says. "I just convinced my agent that if I was modeling, I could definitely do commercials, and if I could do commercials, I could definitely do movies." A slew of TV ads and some bit parts followed. MTV hired her after she sent in an audition tape—even though she had zippo knowledge of rock. "I live for Frank Sinatra, Tom Jones, Al Green and Engelbert Humperdinck," she says. That didn't matter to MTV vice president of production Joel Stillerman. "She's obviously beautiful, obviously smart, obviously funny," he explains, "And she pretty much says party."

Another thing Duff has is a legion of male admirers, including basketball star Christian Laettner, 23, now of the Minnesota Timberwolves. Set up by a mutual friend last spring, the two had dinner at Manhattan's trendy Cafe Tabac, but not alone. "[Fellow VJ] Steve Isaacs went as my duenna," Duff says. She and Laettner have stayed friends—platonically—ever since.

Duff's true ardor is reserved for her on-again, off-again boyfriend of the past year, garage rocker Whitfield Crane of the band Ugly Kid Joe. Though he's often away on tour, when Crane is in town, says Duff, "he makes me happier than Jerry Lewis in Paris."

And she refuses to surrender to the star trip. "I like the inside of me," she says, in typically inventive syntax, "and I think that's kind of what sticks out." According to Duff, she eats "everything," gets $8 haircuts from a "one-eyed barber" and spends more time reading than pedaling an exercise bike. For fun she paints "ugly primitive" acrylics and takes occasional wintry dips in the Atlantic with the Coney Island Polar Bear Club.

Her outlook is best summarized by her dad, Phil Duffy, a developer, who says that, at 13, Karen told him, "I've never had a bad day in my life." She still feels that way. "My whole view," she says, "is that no matter what you're doing, you've got to bloom where you're planted."