Shape-shifting actor Joaquin Phoenix rules as GLADIATOR'S sublimely twisted young emperor -- and finally marches into stardom.

by Chris Nashawaty

"It vexes me...I'm terribly vexed." Bellyache all you want about the sorry state of Hollywood screenwriting, but it takes a certain genius to work the word vexed into a summer-movie catchphrase. Still, it's the delivery that's the real killer. And that, dear friends, Romans, and countrymen, is what brings us to Joaquin Phoenix.

Yes, Russell Crowe may be the blockbuster epic's breakout star--the guy who'll parlay Maximus into a slew of rich offers--but it's his 25-year-old costar Joaquin (pronounced wa-keen) Phoenix, as the deliciously sadistic and paranoid young emperor Commodus, who's the most unexpected revelation.

In person, Phoenix comes across more like a vulnerable ragamuffin than a terribly vexed Caesar: His fingernails are gnawed almost to the cuticles; his jeans hang halfway down his butt; and he sports fresh stitches on his forehead from what he admits was a boneheaded motorcycle accident. Then again, he's just shot three movies back-to-back; he's still jet-lagged from the whirlwind of Cannes (where his upcoming crime drama, The Yards, debuted); and oh, yeah, today he's chosen to quit smoking.

If all that weren't enough, Phoenix also seems freaked out by his new high profile. Sitting on a stoop in Manhattan's Chelsea neighborhood, Phoenix shyly ducks his head when the occasional passerby does a neck-snapping double take. "It's weird--for the first time people in traffic call out to me for an autograph," he says with a laugh. "I guess my other films have had smaller and more specific audiences."

As he says, Gladiator isn't exactly his first gig--just the first that a big chunk of America has shelled out nine bucks to see. The first to get him noticed was 1995's To Die For, in which Phoenix so convincingly played the burnout whom weather girl Nicole Kidman persuades to whack her husband that he claims people thought director Gus Van Sant had discovered him on the street. Phoenix followed that with more scene-stealing turns, as an imprisoned drug dupe in Return to Paradise, a dim-witted Romeo in U-Turn, and a wily porn-store clerk in Eight Millimeter.

"When I met with him for Gladiator, I think his first reaction was absolute horror," says director Ridley Scott. "He said, 'You want me to do a toga-and-sandal movie? You've got to be out of your f---ing mind!' And he actually suggested we test him, which is very smart because he needed to find out if he could do it too." Which raises the question: How many actors would give a director the chance to show them they're wrong for a part? "I don't know how true that is," Phoenix says. "But it is true that no one really saw me [as Commodus], which is understandable because I don't think I'd given any indication that I could handle something like this."

Still, even after he landed the role, Phoenix seems to have held on to that same self-doubt. He worried that the extra weight and pasty complexion he intentionally acquired to convey Commodus' descent into decadence was lost on everyone but himself. "They just thought I was getting fat," he says. "I think Ridley wanted a sexier emperor." Adds costar Richard Harris, who plays his father, Marcus Aurelius: "Joaquin doesn't believe he's good and you have to tell him how f---ing marvelous he is. He says, 'I'm hopeless, they all think I'm as good as River, I shouldn't be in this picture, I should be selling cars, I'm not an actor at all.'"

When Harris' remarks are relayed to Phoenix, his face tightens at the mention of his late brother, River. (It was Joaquin who made the 911 call when River, 23, collapsed from a drug overdose outside L.A.'s Viper Room in 1993.) But he actually gives River the credit for helping him discover acting: "We had always been very expressive as children and encouraged," says the actor who, with his four sisters and brothers (sisters Rain, 27, and Summer, 21, also act), was raised by former missionary parents. "And I think you just start to follow in the footsteps of your siblings. I mean, if someone's listening to the Smiths, you start listening to the Smiths. The same went for acting...."

And apparently petty larceny, too. Brought up as a strict vegan, Phoenix recalls how he and his sister would occasionally steal forbidden candy bars, "just to, you know, rebel and have some chocolate." Joaquin Phoenix: mad emperor, reluctant celebrity, unrepentant shoplifter. Terribly vexing indeed.