NEW YORK &

Jonathan Groff races up and down the aisles through the audience, dripping with sweat, singing his heart out and shaking his long wig with manic glee.




It's the revival of "Hair" at Central Park's Delacorte Theater, and it is Groff's big moment as Claude Hooper Bukowski, the 1960s flower child torn between his anti-war beliefs and duty to serve his country in Vietnam.




His song, "I Got Life," is an ode to self love and youthful swagger, and the 23-year-old actor &

the hottest young star in theater since his breakout role in "Spring Awakening" &

works overtime to sell it, doing something unprintable to the ground at one point and belting such lyrics as: "I got my mouth! I got my teeth! I got my tongue! I got my chin! I got my neck!"




Groff's exuberance spreads throughout the crowd of theatergoers &

some baby boomers in Tie-dye &

who can't help but smile.




"It's almost illegal how much fun we're having on stage, to be perfectly honest," he says in an interview. "It's incredible. ... Everyone just loves each other and we're truly like a tribe, on and off the stage. And (we) just go out there and have a blast and run out in the audience and throw our hair in people's faces."




The actor leads an ensemble cast in the iconic musical that debuted in 1967 at the Public Theater in downtown Manhattan before heading to Broadway for 1,873 performances.




"Hair: The American Tribal Love-Rock Musical" &

the story of a band of free-loving hippies protesting the Vietnam War &

became a cultural phenomenon, thanks to its trippy pop-rock music, risque drug references and a nude scene that raised eyebrows back then, although few might be startled today.




Still, Groff says, everyone wants to talk about "the naked thing." He calls it "the ultimate freedom to stand there and have no clothes on and be your true self."




Well, that's easy for him to say: He stays clothed during the scene.




"If there was any place to get naked, it would certainly be in Central Park doing 'Hair,'" Groff says. "So if I had the opportunity to, I probably would. The show is written so that Claude is confused. He's certainly not as free as everyone else is. It would be wrong for him to get naked."




It was the reverse in "Spring Awakening." Groff had his big break two years ago as rebellious schoolboy Melchior Gabor, and raised his heartthrob quotient as the sole performer to bare his butt in the Tony-winning rock musical, an erotic adaptation of Frank Wedekind's classic German drama about sexually repressed teens.




"I learned a lot about my role in 'Spring Awakening' actually through doing 'Hair,' because 'Hair' is so open and free-with-your-body and lots of upbeat songs and lots of audience participation, and 'Spring Awakening' is so restricted and buttoned-up and knickers and coats," says Groff, who grew up in Lancaster, Pa., in the heart of Amish country.




Groff received a Tony nomination for the role, and left the show in May to do "Hair." He had previously portrayed Claude in three concert performances at the Delacorte last September, and demand ran so high that the theater scheduled an extended encore this summer.




"This show has taught me so much about letting go and living moment to moment, and enjoying where you're at when you're there &

and I'm really grateful for that," says Groff, who waited tables after moving to New York in 2004, and has appeared on the ABC soap opera "One Life to Live."




The production closes Aug. 31, but Groff will be long gone by then.




He leaves Aug. 16 for an even bigger project: a leading role in director Ang Lee's "Taking Woodstock," which begins filming this month in upstate New York. It is based on the memoir by Elliot Tiber, whose parents' motel was the headquarters for the 1969 music festival, and co-stars Emile Hirsch, Imelda Staunton, Paul Dano, Zoe Kazan and Meryl Streep's daughter, Mamie Gummer, among others.




Groff, making his film debut, will play Woodstock organizer Michael Lang. Lee recently cast him after seeing an audition tape, and Groff began rehearsing the role two weeks ago.




"It's insane," he says. "It's really, really, really insane. Something is in the climate, or the stars are aligning or something, because it's like all of this stuff from the late '60s keeps popping back up."




Groff calls this his "Summer of Love," referring to 1967 when tens of thousands of youth made the Haight-Ashbery neighborhood of San Francisco the hub of hippiedome. But he looks anything but hippielike on a recent afternoon in Central Park, sitting on a bench, drinking Diet Coke and sporting a striped polo, jeans and a backward baseball cap.




He is, however, undeniably cute. He's got curly, light brown hair that touches past his ears, a wide smile and a sturdy build that's tailor-made for an Abercrombie Fitch ad. He has a reputation for working hard and playing well with others. A mother would approve.




If he's aware of any of this, he doesn't appear to let it go to his head.




"He's talented and, there he is, working his butt off, you know, just so on it &

willing to try anything, willing to do it again, willing to rehearse more," says "Hair" director Diane Paulus. "Never a moment of attitude from him about anything. ... It's just, like, kind of a deep place of something that he's working from &

a deep resource of energy and interest, and it's great because when you have someone like that, it just spreads in the company."




Groff said that Lee, the Academy Award-winning director of "Brokeback Mountain," sat in the audience a week or so ago with his son, Mason, who recently performed in a high school production of "Hair."




What did Lee think?




"He loved it," Groff says. "He loved the whole thing. He had a blast. His son was up (on stage) dancing with us after it was over. It was really, really fun."




In Groff's groovy life, the stars are definitely aligning.