It was this very uncertain actor who led a party of nine through the woods and to a clearing that featured a majestic waterfall in a big California park that he refuses to identify for fear that the next time he hikes in, he'll find that TMZ has established a bureau there. His dad had shown him the spot years before, and Efron wanted to share it with his friends. He had carefully avoided the poison-oak leaves the whole hike, using sticks to push them away, limboing under hanging branches. When they reached the waterfall, he climbed up the cliff face, which didn't look so bad from below, and before he knew it he was standing 30 feet above his friends and the water below. He freaked. "My legs were shaking," he says. "The pool started to look out of focus. It would get closer, then further away. So I sat down for a minute, but everyone was egging me on to jump. 'Jump! Jump! Jump!' I'd never seen anyone go off this jump. So I was like, 'I gotta do this. I brought everyone here. We made it through the poison-oak forest. I gotta at least do this jump.' " From atop the cliff, Efron determined that if he jumped too far out, he'd crash against the jagged rocks on the far edge of the pool. Maybe he also saw, down there on the rocks, the desiccated dreams of all the "real deal" actors who never panned out. All he needed to do was clear one little poison-oak bush directly below. No problem. He leaped. And the second before he hit the freezing water, he felt an ever-so-slight whoosh tickling his back and hands as the bush branches transferred enough of the dread urushiol oil to eventually spread over every part of his body—even his much-squealed-over teen-idol dick. "That was it," he says of the leap. "The moment I got it."

The cliff jump that gave Efron poison oak.

• • •

Zac Efron is not cool, and this pronouncement is neither an insult nor a revelation to him. His lack of cool has nothing to do with the fact that, as a preadolescent, he lived for community theater or that he tried to get away with wearing a fedora to school at 15. Cool is effortlessness. Efron is all effort. Whether you're the type who watches High School Musical and starts feeling so tingly that you think you've finally gotten your period, or the kind for whom watching it makes you fantasize about living in a European country where euthanasia is legal, you can't view a choreographed number like HSM 1's "Get'cha Head in the Game"—in which Efron and his Wildcats teammates sing while manipulating synchronized bouncing basketballs—and not immediately understand the level of commitment the project would demand of a 17-year-old. "He never quits," says Burr Steers, who directed Efron in the new drama Charlie St. Cloud as well as the 2009 switcheroo comedy 17 Again, a film that featured what seemed like—but wasn't—a special-effects trick with Efron spinning a basketball on his pinkie. "Even the basketball wizards we hired to teach him tricks had never seen that done," Steers says. "But Zac, being incredibly competitive, just practiced every night until his pinkie was calloused and battered. He willed it."

The challenge directors have is to get him to try a little less. Hairspray's director, Adam Shankman, had to tell him that if he really wanted to be convincing as teen idol Link Larkin, he'd better stop beaming so goddamned much. "It's not how I am," Efron says. "Even in my audition I was smiling and happy. Not cool." On the set of 17 Again, Steers felt like he had to break him of some of the nicer habits he'd picked up at the House of Mouse. "It's something you go through with a lot of these young Disney actors," Steers says. "Teaching them that when they're acting, they don't need to worry so much about being polite, about treading gently around other people."

Hollywood, like everything else, is just an extension of high school, with the burnouts and the jocks coexisting uneasily. Burnout Sean Penn drinks and smokes too much and will always be cooler than jock Tom Cruise, whom one imagines doing lots of crunches and high-fives. Same with Shia LaBeouf and Zac Efron. LaBeouf seems to give not one shit. He disses Spielberg and flips pickups and just gets bigger; Efron makes appearances at Bar Mitzvahs as favors to industry friends. "I'm so jealous of that," Efron says of LaBeouf, whom he doesn't know personally. "Yeah, that's awesome to not give a shit. And Shia still pulls it off. That's so cool. It's just awesome. It just comes easy to some people."