From PEOPLE Magazine Click to enlarge
HELLO, I'M JOHNNY CASH.
To pull off his Oscar-nominated turn as the country-music legend, Phoenix shaved off his widow's peak and wore brown contact lenses. But Walk the Line director James Mangold wasn't convinced until he saw his leading man, 31, perform onstage. At first Phoenix, who has no musical training, was timid. "I told him, don't hold the guitar like a baby; grab it by the neck," says Mangold. "When I met John [before his death in 2003], his message was "the guitar is an extension of me.'" So "I started holding a guitar no matter what I was doing," says Phoenix, who took six months of lessons with musician T-Bone Burnett. He also asked people on the Memphis set to call him "JR," Cash's nickname.

EARLY TRAGEDY, PARALLEL LIVES
Both Cash and Phoenix lost older brothers: The singer was 12 when his brother Jack was killed in a sawmill accident, and Joaquin was 19 when his famous sibling River overdosed at L.A.'s Viper Room club at 23. Joaquin—who made the 911 call—never discusses the incident and says he didn't draw on personal tragedy for the part. "It doesn't honor John's experience," he says. "When I read a script, I don't think about whether I've shared experiences." But like Cash, who beat an amphetamine dependency, Phoenix has struggled with alcohol abuse, spending a month in rehab after Walk the Line wrapped. "I just wasn't happy with my drinking," he recently told Elle. "I wasn't like an every-day drinker. But I was definitely using it to relax, take stress away."

DON'T CALL HIM LEAF (ANYMORE)
Phoenix—who went by the name Leaf from age 6 to 16—was reared by Children of God missionaries who frequently moved the brood (which includes Phoenix's three sisters Rain, Liberty and Summer) to locations from Puerto Rico to Oregon before settling down in 1978 in L.A., where they struggled to make ends meet. Still, "even when we had no money, we still had a car to sleep in and a friend's driveway we could park in and a dad who said, "I'm going to take care of you,'" Phoenix told Details. For fun, the Phoenix kids staged musicals outside, which is how a Hollywood agent discovered them.

HIS BIKER GANG
Phoenix's pals these days include actors Robert Patrick, 48, and Balthazar Getty, 31, with whom he became friends while shooting the 2004 drama Ladder 49. "Balthazar, Joaq and I see quite a bit of each other at my house or his," says Patrick, and the trio take their choppers for rides along the California coast (Phoenix owns a Ducati). Says Patrick: "He rides a mean motorcycle."

HE'LL HAVE THE TOFU BURGER
Raised a vegan, Phoenix requested faux-leather costumes for his characters in Gladiator and Walk the Line. But "he's not the vegan police. It's just his thing," says Patrick. At cookouts, "we make sure we've got something for the vegan—a lot of tofu and veggie burgers." Meat eaters weren't turned away from a New Year's bash at Phoenix's L.A. home. "I was given the task of cooking the chicken," says Patrick. "He didn't want to do it, but he did get a barbecue [grill]."

HE WANTS HIS MTV!
"He's very musically inclined," says Walk the Line costar Reese Witherspoon. "And this ignited that part in him." So much so that Phoenix's new hobby is directing music videos, making his debut with a spot for Welsh band People in Planes last December. "He was just a regular dude with a lot of energy," says Planes frontman Gareth Jones. "Every time we got a take right, he would skip and jump around like a little girl." Since then he's been behind the camera for goth-pop group She Wants Revenge. Next up? Rising rockers Ringside, led by Getty.

MAN OF MYSTERY
Phoenix's reputation of being less than loquacious is "a misunderstanding," says Mangold. "He's an incredibly social and gregarious person. He's just extremely cautious in front of a microphone when people are asking him questions." Same goes with pals. "He picks what he wants to keep close to him and private," explains Patrick. "There's still a lot I don't know about Joaq. But what I do know, I love."