By Susan Gerhard

THERE ARE PAINED performances, and there are painful performances. When major actors pour their megawatt celebrity into roles that require IQ reduction or insight into psychological difference, the performances are usually an excruciating combination of both. Think Sean Penn's attempt at mental challenges in I Am Sam, or Jim Carrey's swipe at pathological shyness in Eternal Sunshine of the Spotless Mind, or Mel Gibson's stab at paranoia in Conspiracy Theory (OK, post-Passion, I realize he should have been comfortable in that role), or even Charlize Theron's take on outsider rage in Monster (though I personally believe she was brilliant) – these performances caused many people to cringe. Too much disbelief needs to be suspended when faced with millionaire celebrity odes to marginal states of mind. There isn't enough compassion in the world to fill the chasm between the lifestyles of these rich and famous and the desperation of the individuals their acting pays tribute to. Performers like Jack Nicholson and Will Ferrell, who can bridge the gap, are the exceptions that prove the rule: outsiders, eccentrics, and the mentally unhinged generally need to play themselves.

The genre that seems most capable of accommodating the nonconforming is nonfiction film. It's been building an amazing track record over the past half-century, dating back to Grey Gardens and including the entire Errol Morris oeuvre. It reached a high point with Crumb. It seems to me that few of the best documentaries aren't about peculiarity. It's a genre where the stranger the behavior (say, a president deciding to continue reading a book about goats to an elementary school class while giant buildings in New York tumble to the ground), the more comfortably it fits. We're not about to put up with 90 minutes of normal in a nonfiction film. This is truth, after all. It has to be bizarre.

The documentary Monster Road wedges itself squarely into this tradition. A fascinating merging of three of the more popular nonfiction types these days – artist profile, family excavation, and sociological essay – it tells the story behind the appealingly eccentric, lo-fi work of claymation animator Bruce Bickford. Best known for giving stop-action life to Frank Zappa's music in the '70s, Bickford has created plenty more oddities that haven't, until now, been seen outside his basement. Director Brett Ingram helps Bickford dust off some true obscurities hidden in his cupboards, damaged by dust and spiders, then throws them up for view, in all their mutant glory: bodies being slashed inside out by prison warden-doctors, spilling their very detailed, tiny entrails into the basement of a dungeon medical laboratory, until the torturers get their comeuppance.

Bickford says he inhabits his characters, but you truly understand the Method acting involved when you learn about the tortures Bickford describes in his own life. He was a small kid who climbed trees to escape bullies, then was sent to Vietnam, where he couldn't find trees high enough; he got a knife in his foot during one disagreement. Ingram gently connects the dots – building a Bowling for Columbine-style thesis about how a country obsessed with building bombs is bound to drop a few on its own citizens, psychically at least. It turns out Bickford's father spent his days testing military equipment for Boeing, watching tanks that were to emerge from missiles explode behind safety glass, and coming home at night to comment on the day over dinner with the family. Bickford's father forgets that work now, and most of the rest of his tangled past – he's suffering from Alzheimer's. His handwritten cards litter the walls with the toughest questions (for example: What do we do when the oil is all gone?). His philosophical approach to life makes him the film's unofficial narrator, rediscovering his past one memory at a time. It's one of the most touching performances I've ever seen on film, as the father pierces through his own fog. "We had a bad war," he says.

Throughout, Ingram applies delicacy where other filmmakers might employ a sledgehammer. His interviews are major achievements in a form that too often relies on accusations and defenses. His stop-action landscape photography paints a gorgeous Northwest sky and miniaturizes the rural backdrop as if it too is claymation, which has the effect of wrapping the entire story in a kind of tender magic, one that lets its protagonists retain their well-earned fantasies. Bickford, who's got thousands of little guys stashed in every drawer and crevice of the spacious home he occupies by himself, tells the filmmaker he identifies with Peter Pan. "He was the little guy; I was a little guy," he says, with hope. "Maybe the little guys could survive."

'Monster Road' runs Thurs/23-Mon/27, 7:15 and 9:15 p.m. (also Sat/24, 2 and 4 p.m.), Red Vic Movie House, 1727 Haight, S.F. $5-$7. (415) 668-3994.