Imagine for a moment that you're a documentary filmmaker, fortunate enough to land one of independent music's most creative people as your next subject. The story of his life is fascinating, the music and paintings he's created promise a feast for your film's visuals and soundtrack, and artists from Beck to Death Cab for Cutie to Johnny Depp will give you free publicity with their endless shout-outs to him.

Imagine that your subject has documented much of his own existence and is so eager for your movie that he's made all of his footage and music available to you.

Now imagine that your subject is a manic-depressive, mental hospital regular -- someone who could go off the deep end as sure as he could suddenly sing the most beautiful song you've ever heard. Welcome to the world of Jeff Feuerzeig.

"He has hurt people. He crashed his father's plane once when he thought he was Casper the Friendly Ghost," said Feuerzeig, who directed the new rockumentary "The Devil and Daniel Johnston." "He tested me. We were at George Harrison's vigil in Central Park when George Harrison passed away. It was very sad. Daniel is probably the world's biggest Beatles fan. We went to the vigil, and Daniel just didn't want to be there that day.

"He pointed at the roof of the Dakota, where John Lennon used to live, and he said to me, 'What would you do if I jumped off that building?' " the director said. "I looked him in the eye, and I said, 'I'd film it.'

"Then he respected me."

Respect is one thing 42-year-old singer/songwriter Johnston has never had any trouble acquiring. Happiness, however, has proven to be more elusive. Living in the basement of his parents' Virginia home in the '80s, he used a cheap boombox and an old piano to compose hundreds of melodic, intricate songs often interrupted by his mother's shrieks that he should get a real job. The tapes eventually found their way into the hands of some influential people, and Johnston seemed on the verge of stardom, even as he worked a day job at his local McDonald's.

Then Daniel Johnston lost his mind.

"He's like (the Beach Boys') Brian Wilson or (Pink Floyd's) Syd Barrett because he suffers from manic-depression," Feuerzeig said. "But when you listen to Pet Sounds, there's no warning label that says 'This music was written by a guy who was mentally ill.' And when you listen to Daniel Johnston, you shouldn't listen to it in that way either."

After numerous incidents that saw him running away with the circus, vanishing among the homeless, and harming others while trying to save them from the devil, Johnston's hospital stays became more permanent in the early '90s. Around the same time, grunge took over the music industry, and one of the world's biggest rock stars began giving shout-outs to an obscure man in a padded room.

"Those raw recordings, and their lyrics, were so strong that they touched people like Kurt Cobain," the director said. "He wore Daniel's frog T-shirt [from Johnston's album] Hi How Are You on the MTV Video Music Awards, and he was Kurt Cobain's favorite singer/songwriter."

Now after decades of bidding wars, flirtations with success, and near-fatal setbacks, things have come full circle. What remains is a gifted madman and his enormous catalog of infectious pop songs. And it's all documented in a film that is as beautiful, random and unsettling as its subject.

"[Butthole Surfers frontman Gibby Haynes] had the day off, and he said, 'I'm getting seven cavities filled. Why don't you interview me in the chair?' " the director said of one of the film's bizarre moments. "In between each cavity in his horrible mouth, in between the drilling, we would ask a few questions."

Another odd call: Feuerzeig's decision not to interview Johnston for the film. "I made an internal monologue out of his tapes because, no, Daniel is not interviewed in his own film," he said. "Daniel cannot host his own film like R. Crumb did in the movie 'Crumb' or Isaac Mizrahi did in 'Unzipped.' ... Daniel Johnston cannot do that. Thank God he recorded those tapes, and we are able to experience his journey in the moment. Because let's face it: Sound is much more important than picture."

If you want to depict creative madness, it seems, you have to go down some unpredictable paths. Appropriately, "Devil" is filled with animated paintings, grainy video and Johnston's own obsessive recordings capturing moments like the time his unrequited crush said "I love you" into his tape recorder. Now that the nearly 15-year process of making the film is finished, Feuerzeig once again finds himself proving that he is worthy of Johnston's respect.

"I'm just happy that he's alive to see it happen and to see the film," Feuerzeig said. "He's excited that 'The Devil and Daniel Johnston' is coming out into theaters and that people all over the world can now listen to him and collect his drawings. His art is really exploding.

"He tours the world, he goes to festivals all over Europe, and there are thousands of kids who know all his songs and do sing-alongs," the director said. "He does sold-out shows all over the United States, and he's not dangerous anymore because he's medicated. He stays on his meds and he's fine."

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