HOLLYWOOD — Emile Hirsch woke up at the edge of his bed after weeks of filming "Into the Wild," shouting into what he thought was the Grand Canyon, convinced that director Sean Penn and his crew had abandoned him to test his endurance.

"Sean's really pushing me now," he thought. "How could they do this to me?"

Even after he registered the blank hotel room walls around him, Hirsch wasn't sure what town he was in. The monthslong shoot had taken them to locations from Mexico to Alaska. It was starting to wear on him.

But it wasn't like Penn didn't warn him. As Hirsch recalled it, Penn was visibly relieved when he accepted the part. "You're a good guy," Penn told him. "You've got a good head on your shoulders. ... I'd feel bad about what I was going to put you through if you were really tortured at the get-go."

"Into the Wild" set a new threshold for Hirsch. He dropped a quarter of his body weight for the part of real-life adventurer Christopher McCandless, who in 1990 set out alone on a two-year cross-country trek, eventually heading for the Alaskan wilderness only to starve to death four months after he got there. Hirsch ran 20 miles a week. He canoed river rapids. He came face-to-fangs with a grizzly, take after take. He carried a 30-pound pack much of each day. Even in waist-deep snow. And he joined the small crew in a weeklong campout on the Colorado River — macho stuff for an actor whose most daring on-screen challenge up to that point had been shaving his head for "Lords of Dogtown." And as that film's director, Cath-erine Hardwicke , remembered it, even that took serious coaxing.

But Hirsch said he was so pumped up while filming "Into the Wild" that the physical exhaustion, that he was working for one of his idols, that the role could launch him as a leading man, didn't really get to him. He just felt lucky.

"I believed in what I was doing so much that I was never really nervous in ways that I've been on other projects," he said.

Indeed, Penn had envisioned Leonardo DiCaprio in the part 10 years ago, when he first read the book. But by the time he got the movie rights, DiCaprio was too old for the role. Hirsch, however, was just the right age. "On the cusp of going from boy to man," Penn said.

At the time, Hirsch had finished "Dogtown," a feature inspired by the 2001 skateboarding documentary "Dogtown and Z-Boys." Penn was moved by Hirsch's performance as the brooding but sensitive skateboard pioneer Jay Adams.

"Into the Wild" and Hirsch, specifically, already have earned high praise and Oscar buzz. And "Speed Racer, " the Wachowski brothers' live-action version of the 1960s anime set for release in May, no doubt will mark Hirsch's coronation. It's a heady time for the 22-year-old, but he said he's prepared for whatever comes.

"I think I'll just stay pretty similar to how I have been," he said. "Pretty mellow, you know?"

To prepare for "Into the Wild," Hirsch pored over McCandless' tersely written journals. He read some of McCandless' literary idols, like Henry David Thoreau and Jack London. He visited McCandless' parents and spent a few days with his sister.

He also trained and dieted relentlessly. He got so thin, Hardwicke said, that she seriously suggested he talk to Christian Bale — who became emaciated for "The Machinist" — about staying healthy.