SUNNY NOAH'S ARC OF FAME By LARRY WORTH ------------------------------------------------------------------------

AFTER three years as Dr. John Carter on TV's "ER," Noah Wyle has become a heartthrob to millions.

But to alumni of St. Thomas' pre-school in L.A., he'll always be a troll. Actually, that's a testament to the acting skills of a certain 5-year-old who nabbed the villain's role in his class' production of "The Three Billy Goats Gruff."

"I don't think there were any critics present," Wyle deadpans, before flashing his trademark impish grin. "I'm only thankful that kids aren't as mean as critics." A second later, he takes that back, recalling how fellow St. Thomas pupils mercilessly taunted him every rainy day.

"They'd yell, "Hey, Noah, where's the ark?'" he says, perfectly mimicking a child's sing-song chant. "But that only made me embrace my name and start collecting Noah's Ark memorabilia."

Over the next 21 years (he turned 26 on June 4), Wyle further honed his ability to find positives in the negative. That's been true professionally and personally.

Exemplifying the latter, 8-year-old Wyle - galvanized by his older sister and younger brother - dealt with Mom and Dad's divorce by embracing a stepfather and three step-siblings, then a stepmother and half-sister. "Hey, it's twice the holidays and twice the gifts," he says. "We have the best Thanksgivings you could ever imagine."

And that, Wyle realizes, is the perfect segue to what's brought him to the Regency Hotel: promoting "The Myth of Fingerprints" (opening Wednesday). The film marks his debut as a big-screen leading man and associate producer.

The story, which co-stars Roy Scheider, Blythe Danner, Julianne Moore and Brian Kerwin, concerns a Thanksgiving Day reunion for a family that's gone its separate ways. But that's not to say Wyle ever confused his screen character and personal life.

"You'd think in any kind of family drama that you'd cull from your own experiences and draw parallels to the script," he says. "As an actor, I'd do that only as a last resort." So did "ER" force him to "the last resort?" No, but Wyle's reality and Dr. Carter's reality became virtually one and the same as soon as the show hit the airwaves.

"Both of us were starting something new, both were thrown in completely over our heads, both had to react to circumstances well beyond our control, and both had to make the best of it," he says.

Wyle had acted in four films, each featuring an ensemble cast ("Crooked Hearts," "A Few Good Men," "There Goes My Baby" and "Swing Kids") before co-starring with George Clooney, Anthony Edwards and the rest of Cook County General Hospital's "staff."

As anyone with a TV set knows, the show became an instant sensation, along with its stars. And though watching his public profile go from zero to 60 wasn't easy, Wyle got transition tips from his "TV shaman," Clooney.

"Along with advice on ways to cope, George said it's the rarest of cases when you have actors with such similar work ethics, senses of humor and levels of professionalism," Wyle recalls. "You figure it couldn't possibly be true that we all like each other. But we do, just as we all know that "ER' is the gift that got us everything we ever wanted."

That's one reason Wyle was so receptive to Clooney's idea to do a live broadcast of the "ER" fourth season opener, scheduled for Sept. 25. (He admits to being "nervous, excited and intrigued" by the concept.) But he's surprisingly pragmatic about the show's future.

"I grew up watching "L.A. Law,' which, at that time, was the most fashionable show around," he says. "And one day, it was simply deemed out of fashion. It died a very slow and ugly death, the same way "ER' will probably die. That's just the nature of the beast."

Wyle is equally savvy about the way people fawn over him. Wherever I go, everybody - and I mean everybody - couldn't be nicer to me," he says. "But I realize I'm probably not getting the most honest representation. It's kind of unsettling. "But I'm not complaining. My privacy has stayed mostly intact, and I have a rewarding and fulfilling home life."

Speaking of which, Wyle says he's found true love with Traci Warbin, a makeup artist he met on the set of "Fingerprints." Having recently returned with Warbin from a trip to Bora-Bora (where Wyle devoured Kurt Vonnegut's entire canon during "hammock time"), they're on the verge of getting engaged.

"Things are going so well that I'm just waiting for the other shoe to drop," he says. "I keep looking over my shoulder to see when all this good karma is going to end. That's why, even if I'm savvy about the future, I'm glorying in the here and now."