If you've watched an episode or two of "Dharma & Greg," you already know a little about onetime "Valley girl" Jenna Elfman since she's the first to admit that she throws much of herself into the character.

For starters, Elfman is tall. (5 feet, 10 inches, barefoot.) She's a little loopy. (She recently delayed an interview so she could engage Richard Dreyfuss, her co-star in the new film "Krippendorf's Tribe," in a "tickle fest.")And she's incredibly passionate about her work, her husband, her lighting technicians, her favorite pastry ("those little ones with the powdered sugar and honey - so good!"), her new home in the Hollywood Hills . . . and, well, we could go on forever.

The list never stops, mostly because Elfman - like Dharma - never stops enthusing about everything in her life. That's the appeal of her show, and that's the appeal of the woman.

In a world full of cynicism, neuroses and insecurities, Elfman is unabashedly joyful and completely certain about who she is and what she wants to do with her life. She's hap-hap-happy. And she wants to make everyone else happy, too.

"I've had this purpose since I was little," Elfman, 26, says. "I thought about being a nun when I was a kid because I loved people so much. Nuns help people in front of them, which is such a beautiful thing. And now, with what I'm doing, I can communicate with millions of people at a time, setting an example hopefully for the better and the good, and if I can do that - oh boy! - that thought just makes me weep."

From some people, such uninhibited idealism might come across as somewhat suspect and more than a little annoying. But Elfman is the real deal. Everyone she meets seems to come away from the experience touched in some small way.

"Jenna is a joy and a delight and a source of light in my life," says Todd Holland, who directed Elfman in the new comedy "Krippendorf's Tribe," which just opened.

"I think she has made a conscious decision to look for joy and happiness in life, and you can see that by the way she lights up the room. I know that sounds corny, but it really is true. The camera picks it up, too. I think she has an incredible career ahead of her."

Elfman is off to a pretty good start. The weekly lovefest that is "Dharma & Greg" is the rare freshman series to win an audience based on its merit and not its time slot. Now, she can be seen with Dreyfuss in "Krippendorf's Tribe," a no-holds-barred farce that showcases Elfman's boisterous comic style. And Ron Howard just cast her opposite Matthew McConaughey for his next film, "Ed TV," in a role that just about every young actress in Hollywood wanted.

"When I left the audition, Ron told me, `You are so good,' " a beaming Elfman remembers. "I was floating. Then he canceled the rest of the auditions and gave me the part. I couldn't believe it. Life is just so good now."

Now and just about always. But the blissed-out Elfman nearly didn't make it into this world at all. Her mother contracted pneumonia during pregnancy, and it reached a point where one lung was full of water and the other wasn't too far behind. Doctors told her they could save her or they could save the baby - not both.

"Mom didn't listen, and during childbirth, there was not one complication," Elfman says. "I think that's one reason I've always been passionate about life. My mom had it. She was determined to survive and have everything be OK and I think from inside that little old womb, I was, too."

Elfman grew up in Northridge, her father working at Hughes Aircraft and her mother staying at home with the three kids. She always loved performing, whether it was playing a tulip in the school play or break dancing on a piece of cardboard in the middle of her residential street to the amusement (and bemusement) of her neighbors.

"Home was always an incredibly safe place for me," Elfman says. "And I was a total valley girl. I'd go to the Northridge mall and then go over to the water slides at Nordhoff. Then there was the Greek Festival at St. Nicholas, which is where I went to school for five years. They had the best food there, stuff you would die for."

Elfman did most of these things with girlfriends. She describes herself as a "geeky girl" in high school who didn't kiss a guy until she was a senior. Ballet was a passion, but ligament damage in her ankle made the exercises painful. She applied and was accepted to Seattle's prestigious Northwest Ballet, but she never went. She didn't know what to do.

After high school, Elfman (occasionally) attended California State University, Northridge, for 11/2 semesters and worked as a grocery bagger at Hughes Market in Granada Hills but spent most of her time hanging out with friends, partying, staying out late and sleeping in the next day. You know she was in deep when she confides that she knew the words to every song by Warrant and Whitesnake.

Her slacker days ended when she met her future husband, Bodhi (how's that for a Dharma-esque name?) at an audition for a soft-drink commercial. For Elfman, it was love at second sight ("Even though he was immediately telling his friends that he had met his future wife," she says) and the relationship coincided with a realignment of priorities. It was no longer enough to dream of success. It was time to will it into happening.

Elfman got commercials. (Toyota and Clearasil.) She studied acting. She danced on the Academy Awards. She became a Scientologist. She danced - briefly - in fishnets on a ZZ Top tour. ("I couldn't keep doing it after I looked out in the audience and saw a 10-year-old boy on his daddy's shoulders grooving to me and my leather G-string.") She got an agent and a scene-stealing role on the short-lived ABC sitcom "Townies." Then she got "Dharma & Greg," which figures to be anything but short-lived, and - voila! - success was willed into reality.

"I have an intense desire and intention to win," Elfman says. "I wrote a letter to (ABC Entertainment president) Jamie Tarses before `Dharma & Greg' premiered, saying I was going to give her and the network a hit show. And we have fulfilled that. And fulfilling one's promise is a great achievement. I couldn't be prouder."

Elfman is extremely goal-oriented, saying dreams are necessary for perfect happiness. Otherwise, she says, you drift and put yourself in danger of becoming another show-biz casualty, like River Phoenix.

"You have to keep setting goals and then working your ass off to achieve them," Elfman says. "That's one of life's biggest, most satisfying sensations. It's a shame that people aren't taught, either by their parents or religion, that you have to keep setting goals and keep challenging yourself, especially when you're so able. That's how I approach each day. I'm excited. I'm looking forward to thinking about what I can achieve."

Elfman stops herself and apologizes for the "Tony Robbins sermon." But she doesn't stop for long, not that you'd ever want to cut her enthusiasm short.

"Genuine passion can be contagious," she says. "I had this woman who's dying of cancer write me a letter saying the only time she forgets about her sickness and gets more hopeful and actually sees a future in beating it is when she watches my show."