The odd couple

LOS ANGELES -- Reese Witherspoon gets about 60 seconds to be her professional self, and she uses each one judiciously. She's here to sell her latest movie, the Johnny Cash biopic ''Walk the Line," and she gets right down to it. In a demure black dress and diamond cross necklace, her blond hair soft but styled, she's an American sweetheart straight from central casting.

Then her costar -- the star of the movie, the young man playing the Man in Black -- bounces into the room and all bets are off. Joaquin Phoenix has no agenda, except maybe to amuse himself and exhaust the clock. He cracks gum. He hums. He dances. His impossibly baggy jeans and ratty red sweatshirt only hint at his indifference.

Witherspoon can't help laughing. Reputation for integrity aside, she can't resist getting sucked into the silliness. The two just finished playing man and would-be wife, and, like many married couples, she and Phoenix now have a rhythm all their own. Still, they come off more screwball comedy than king and queen of country. Their initial exchange sets the tone:

''I always want to know what's on your hand," Witherspoon tells Phoenix, who indeed has words scrawled in black up and down his hand.

''I'm too embarrassed to do interviews," he responds, apparently to a question only he has heard.

Witherspoon: ''Why? I'm really friendly."

Phoenix: ''I know, I've worked with you. Ugh, argh, all right."

Witherspoon: ''I don't have cooties."

Phoenix: ''Cooties!"

Witherspoon: ''If I did, you'd have them by now."

Beside cooties, other subjects they discuss include a vintage photograph of Los Angeles traffic that's hanging on the hotel wall, whether his nickname is really Kitten (it's not -- that was a joke he made years ago that keeps getting reprinted), whether he does in fact pay friends to scream his name at events (another joke he wishes he hadn't made), whether they should make a sister-brother buddy movie together (''You'll be like my pesky brother," Witherspoon decides. ''I like that," Phoenix says. ''I want to be like your cute younger brother, like, 'Oh God, it's him again.' "), the correct pronunciation of Phillippe, her actor husband's last name, and whether Ryan Phillippe is as perfect in person as he is on paper. (''That's a good-looking kid," Phoenix teases, while Witherspoon rolls her eyes in mocking agreement. ''Nice personality, nice eyes, hobbies, what more can you ask for?")

They take their own time, but eventually they do get around to ''Walk the Line," which opens Friday. Neither is a natural braggart, but it's obvious they're proud of their work. He plays Johnny Cash, she plays June Carter Cash, and both capture the essence of their characters, if not their exact mannerisms. Theirs aren't impersonations. They're adaptations. That's a good thing, since they do all their own singing, an act of courage considering the Cashes were country superstars before they died within months of each other in 2003.

The two, in fact, signed on to ''Walk the Line," which documents the early Cash careers and courtship, without knowing whether they'd be singing or lip synching. They also insist the producers and director/co-writer James Mangold never asked them whether they could carry a tune, or play an instrument, or fall in love convincingly between songs and other on-screen marriages. There were no screen tests or test recording sessions of the sound that Johnny Cash made his own in the 1950s.

''I wouldn't say I was a fan" before filming, says Witherspoon, who grew up in Nashville, the country music capital of the world. ''I got all the albums, got every videotape, read every book, every article, called everybody in Nashville to get more tapes, more books. When I signed on to do it, they didn't tell me I would sing. They didn't know I could sing."

''That was their hope," adds Phoenix, who met June and Johnny Cash at a dinner party before he was formally cast in the role. ''But I certainly couldn't say, 'Yeah, I could pull it off.' In my mind, it was to be decided. It wasn't like, 'No matter what, you're going to sing.' "

They were sent to a musical boot camp of sorts with T-Bone Burnett, the famed roots-rocker behind the soundtracks to ''Cold Mountain" and ''O Brother, Where Art Thou?" They learned dozens of Cash songs. By the time filming rolled around, his voice was noticeably lower and she'd mastered the swooping gulp that characterizes some country music. He could also play guitar without glancing at the chords. She could strum an autoharp convincingly. Their duets onstage invoked the originals: raw, intense, of an era but also timeless.

Talk of Oscar nominations began almost immediately. Among themselves, however, the deal was never to compliment each other's performances.

''He and I both agreed at the beginning that we weren't going to compromise," Witherspoon says. ''We have similar personalities in that I don't think you constantly congratulate yourself on what you've done or what you're going to do."

Phoenix: ''I love me!"

Witherspoon, continuing: ''Let's just get this straight. I'm not going to tell you you're good, and you're not going to tell me I'm good. We're just going to keep our heads down and go to work."

The work has been part of their lives since both were young. Now 31, he's been acting since adolescence, with his breakout role in ''Parenthood" 16 years behind him.

At 29, Witherspoon has been acting just as long, becoming best known for 2001's ''Legally Blonde" and then its sequel. But that's where most similarities end.

Phoenix is famously the son of hippie missionaries who lived in Central and South America before settling in Los Angeles, the brother of the late River Phoenix, and a lifelong vegan who nonetheless smokes cigarettes and did a stint in rehab earlier this year for alcohol abuse. He's nobody's definition of the classic good boy. Many of his roles reflect that. Playing a man/boy obsessed with Nicole Kidman in ''To Die For" made him a critical favorite; playing the paranoid emperor in ''Gladiator" only underscored it.

Witherspoon, on the other hand, is as all-American as they come, at least on the surface. The daughter of a military surgeon and a registered nurse, she spent her earliest years in Germany, where her father was stationed. The family settled in Nashville, where she took up modeling and began acting in local commercials. By 1990 she was making movies while attending an all-girls high school. During a stint at Stanford University, she pledged a sorority. Having met her husband at her 21st birthday party, she's now the mother of two young children.

But even Witherspoon isn't all lightness. Egged on by Phoenix's insouciance and impatience, she complains that interviewers expect her to be something she's not.

''I named my company Type A Films, and I wish to God I'd never done that," Witherspoon says. ''Everywhere I go, every interview, it's 'Are you highly organized?' 'Are you bossy?' And I'm not. It's not me at all."

This somehow leads Phoenix to joke that he has 16 kids in another country and an ex-wife who hates him. (For the record, he has none of those.) ''That was such a horrible, horrible thing to say," he says.

''Let's vilify him, make everyone in America really dislike him," Witherspoon adds. ''No, he's really nice to me. Really generous."

Then again, it's really hard to get him back to the subject at hand. Even Witherspoon, who has played some seriously anal-retentive characters, can't keep Phoenix in line. Suddenly he's in a corner of the room, swinging his hips and tossing his arms and proclaiming it his ''new sexy dance." (''Right on," Witherspoon says wryly.) Next he's lighting a cigarette and blowing smoke in the mirror. His self-discipline, it seems, is reserved for the movies.

''I'm there to service a director and to bring his character to life," explains Phoenix, who says he knew he was making progress when he could shoot an entire concert scene without once thinking about his voice or chord changes. ''[The director] was like, 'Yeah, I don't want impersonations of John. If people want to hear Johnny Cash, they have his records, and if they want to see Johnny Cash, there are documentaries.' So that was freeing in a sense."

That freedom, however, only came after the initial panic of getting their parts, the costars agree. Back then, he was too embarrassed to have her hear his vocal warm-up sessions: La la la la la. ''Jeez, it was the most humiliating thing in the world," Phoenix says. Eventually, though, the two could stand before a mike and make real music.

''It wasn't like I had to perform like John or there was a specific way you had to perform," Phoenix says. ''It was just like, let's play songs."

And play they did.

Lynda Gorov can be reached at lgorov@aol.com.