Joaquin Phoenix wasn't much of a singer, couldn't play guitar, and refuses to wear leather, and that's not a promising start when you're determined to play country music's original bad boy, Johnny Cash.
"I knew I wanted to do the movie without even reading the script," says the 31-year-old actor, who sang all his songs in "Walk the Line" without dubbing, and even learned to strum a few chords.
"I just had a good feeling about it," Phoenix says. "The idea of playing such an interesting, complex character that had an incredibly rich life was overwhelming."
Phoenix stars alongside a brunette Reese Witherspoon, who plays June Carter, Cash's second wife. And like her leading man, Witherspoon learned to sing and play the autoharp.
While a movie about one of America's greatest music legends seems like a no-brainer, "Walk the Line" took a long circuitous route before ambling into theaters. It took four years for producers to secure the story rights from Cash's family. Then, it took another four years to get the film made.
One thing kept the project alive: Cash and Carter, who both died in 2003, gave their nod of approval.
Phoenix says it was an amazing challenge. Cash was a larger-than-life personality who battled drug addiction, and brushes with the law before becoming a musical champion for the downtrodden, a man who recoded some of his finest music in live performances at prisons, before wildly receptive audiences of convicts.
By 1970, Cash was so widely admired by a broad spectrum of Americans, he counted both President Richard Nixon and Bob Dylan among his fans and personal friends.
Before filming began, Phoenix said that writer-director James Mangold gave him this simple advice: "He said to me, 'You're not Johnny Cash and you're not going to be Johnny Cash. It's your interpretation that I want to capture.
"If people want to hear Johnny Cash, he's made a couple of records."
Mangold -- who also wrote and directed "Girl, Interrupted" -- interviewed Cash extensively in the final years of his life, and said that he left very specific instructions about how he wanted to be depicted.
"One of the things John told me about whoever was going to play him was, 'I just hope they know how to hold the guitar. You don't hold it like a baby and you're frightened it's going to break. You grab it by the neck'," Mangold recalls Cash saying.
"So I knew that Joaquin had to approach his guitar like it was something he had lived with all his life -- and that's what he did."
Cash never met Phoenix, but he gave his enthusiastic approval, recalling the actor's Oscar-nominated performance in "Gladiator."
After months of completely submersing himself in the music, the 5-foot-8 Phoenix was able to step into the shoes of the 6-foot-2 star and finally utter his famous greeting, "Hello, I'm Johnny Cash."
At the height of his career, that greeting was almost a guaranteed laugh to kick off any Johnny Cash concert. This was a man so unmistakable he needed no introduction at all. But Phoenix uses those very same words as he depicts a teenaged Cash introducing himself to Sun Records producer Sam Phillips, for what leads to his big break as a singer-songwriter.
Phoenix has the reputation for throwing himself deeply into performances, and since his breakthrough in "Gladiator," he's earned good notices in "Quills" and "To Die For." But he also has the reputation as one of Hollywood's most idiosyncratic characters.
A strict vegan, he won't wear leather. Even for his sword-and-sandal epic with Russell Crowe, "Gladiator" costumers had to outfit him in synthetics. Phoenix even held the line even while portraying Cash, a man who had a soft spot for black leather.
But while he could take some liberties with the costuming, Phoenix knew the same could not be said for the vocals. "Music is always part of how John communicates what he's feeling and seeing," he says. "And that couldn't be faked."