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As the 17 million fans who tuned in to the Aug. 17 premiere of High School Musical 2 know, the fictitious romance of East High students Troy and Gabriella is of the very old-fashioned sort; it took all the way through last year's blockbuster High School Musical and most of the sequel—the most watched show in cable TV history—for them to sneak in a first kiss. Luckily, their real-life counterparts didn't have to wait so long. While they were shooting the first movie in 2005, a real-life romance quietly blossomed between teenage stars Zac Efron, 19, and Vanessa Hudgens, 18. And as they waited for a table on a busy Saturday night at Takashi restaurant in Salt Lake City, where they were filming HSM2 this spring, they were still going strong. "They were sitting on each other's laps and holding hands," says hostess Teal Gibo. "It was really cute."

Hello, Zanessa. For their millions of fans (yes, they've already given the couple a moniker), the young love between Efron and Hudgens just adds to the generation-riveting appeal of the HSM movies, the biggest thing to happen to teen love stories since Grease—minus Grease's smoking, drinking and teen pregnancy. The squeaky-clean Disney Channel movies have spawned the No. 1 album of 2006, a sold-out 42-arena concert tour, an ice show and now plans for a third installment to be released in theaters. At the center of it all, Efron and Hudgens have kept their romance scrupulously low-profile. On the HSM2 set, "if you didn't know they were dating, you wouldn't know they were dating," says a production source. "They're really good at not being obvious." They became more open as news of their relationship gradually leaked out: Witness his megawatt smile and thank-you kiss for Hudgens when she brought him a plate of food at a recent photo shoot. And why hide? "Two people fell in love," says costar Monique Coleman. "Who cares? We're good kids."

Like teen idols from a gentler era, Efron and Hudgens get spotted out buying Pinkberry frozen yogurt, not stumbling out of nightclubs. They hit the gym together and join fellow cast members for movie nights. Bart Johnson, who plays Efron's HSM father, recalls seeing the two at play in Toluca Lake, Calif., where Efron has his own apartment near his family's home (Hudgens lives with her parents in L.A.): "Vanessa had a scooter and she'd pull Zac around on his skateboard with a rope. He'd surf behind her all the way around Toluca Lake."

So why keep the romance so quiet? "First of all, they are so young, still teenagers," says the HSM source. "But it's also the classic teen-idol thing. It kills the fantasy when a teenage girl knows her idol has a girlfriend. But ironically the fans seem to be accepting their relationship, I think because it goes along with the storyline in the movie." Still, Hudgens and Efron maintain a "no comment" policy on the friendship rings each wears. And they were careful to arrive separately to the premiere of Efron's movie Hairspray in L.A. on July 10. But sitting next to each other in the theater and later at a party, the two were hand-in-hand—just as they had been in a private moment in the green room before the MTV Movie Awards on June 3. And at HSM2's premiere at Disneyland on Aug. 14, neither could resist wrapping an arm around the other. While they both refuse to discuss details about their relationship, each is effusive when praising the other. "He's an amazing guy," Hudgens said at the L.A. premiere. And as Efron told PEOPLE during filming, "Vanessa just brings sparkle to everything."

There was no hiding their chemistry when the two took a vacation together in Hawaii in April. Staying at the Fairmont Kea Lani on Maui's Polo Beach, the couple splashed around in the surf, seeming more grown-up as they kissed and embraced. (Rumors they broke up after a fight later that month were untrue, sources say.) His girl, Efron told Rolling Stone, is "a very, very sexy woman." Speaking of his so-called friendship ring, he blushed.

At heart, the biggest teen stars on the planet remain two low-key kids who were raised by middle-class parents (see box) and like to do pretty much the same things they did before they were stars. While filming in Utah, they hung out and watched ... and watched ... and watched ... Anchorman ("Will Ferrell is a God," says Efron), worked out ("Zac goes to the gym almost every single day," Hudgens told PEOPLE on the set. "I try to go with him, like that's my motivation, but sometimes I'll be like, 'Forget it'") and on one occasion whaled on each other. "Once it was snowing, and Zac was on the phone, and I got a huge snowball and, like, hit him with it," said Hudgens, laughing. "We had a snowball fight all the way to rehearsal." These days, they've been known to stop into Robeks in L.A. for a juice after working out and to shop together. On a recent trip to the Gap in New York City, Efron—who stirs the kind of teen hysteria once reserved for Justin Timberlake—gave a 7-year-old girl an autograph, a hug and a wink. But older groupies be warned: "I am," Hudgens told PEOPLE last year, "the girl who will get jealous."

She is also the girl who will drive her boyfriend nuts with her three closets devoted entirely to shoes. Her paydays go towards expensive bags by Balenciaga and Louis Vuitton and her favorite Christian Louboutin stilettos. Efron, meanwhile, has directed his extra cash toward the bill on his first bachelor pad—a small two-bedroom apartment where he sleeps on a mattress on the floor—and used jeans. "I can get, like, eight pairs of $3 jeans," he says. "Who cares if they don't fit? I can give them back to the Goodwill. It will cost me less than one half of Vanessa's pairs of nice shoes." Personality-wise, she's the more intense, reserved one, while he's more mellow and outgoing. "He's at her whim," says the HSM source.

Venus, Mars, same as it ever was. What the future holds for the teenage It couple is far from clear. Before landing HSM, Efron had been accepted to the University of Southern California but deferred his enrollment. Hudgens says she too wants to go to college. But for now both are focused on work. Hudgens dreams of playing Maria in West Side Story, while Efron could use a break from the chick-flick stuff. A fan of Arnold Schwarzenegger and the Rocky and Bourne movies, he'd like to be in something he'd actually watch. As he told Time of HSM: "I couldn't get through the first one." Still, both he and Hudgens are in talks for the third installment. Calling himself "lucky" to be part of HSM, Efron said, "If they still want me, I'd be honored." So there's gratitude—and then there's the girl. "Working with Vanessa was a dream come true," Efron says. Adds Hudgens: "When you get to sing with someone you care about, it's magical."

ZANESSA 101

He was a self-professed "nerd" and straight-A student. She admits preferring shopping to hitting the books. Both had their first kiss around fifth grade. Study up on the couple ...

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  • Contributors:
  • Reported by Jenny Sundel/Salt Lake City,
  • Liza Hamm/New York City,
  • Lesley Messer/New York City,
  • Christina Tapper/New York City,
  • Jen Garcia/Los Angeles,
  • Jessica Herndon/Los Angeles,
  • Amy Elisa Keith/Los Angeles,
  • Jessica Maidson/Los Angeles,
  • Monica Rizzo/Los.