“I’m really angry,” Conan O’Brien says dryly at the beginning of Rodman Flender’s documentary “Conan O’Brien Can’t Stop.” Only this isn’t the baby-faced, rail-thin, happily self-effacing spazz we’ve seen on TV; this Conan is pudgier, more fatigued, sporting a modern-day hipster’s lumberjack beard that looks regressive on his 48 year-old face. Recorded just prior to and during Conan’s two month comedy tour, which followed his notorious fall from grace as the shortest-lived NBC Tonight Show anchor, “Conan O’Brien Can’t Stop” is a scintillating look at a once-gleeful pop icon at his most deflated and vulnerable.

In June 2009, O’Brien graduated from Late Night on NBC, replacing Jay Leno on the Tonight Show and knocking him back to an ill-conceived 10 PM slot; seven months later, due to poor ratings all around and complaints from NBC affiliates, Leno’s show was moved back to 11:35 PM, and O’Brien was asked to take a 12:05 AM slot. He refused, pointing out that an after-midnight slot isn’t “the Tonight show,” and walked away with $45 million. Not too shabby—most of us would have jumped at such an opportunity, and we wouldn’t get squat if we turned it down. But as the movie makes clear, Conan O’Brien is a wreck without an audience. When the filmmakers ask him if he’s ever happy out of the spotlight, he glares at them, and he doesn’t seem to be joking around. For the first time, Conan’s freakish height, his chuckle-under-the-breath Irish humor—laced with contempt even when goofily self-mocking—is more intimidating than funny.

His anger certainly spills into his stage show. During his tour, he performs several snarling blues songs, such as “Polk Salad Annie,” and though he often changes the lyrics for satiric purposes, he appears to be putting his heart into it. Many pasty white comics (John Belushi, Dan Aykroyd) got their rocks off imitating far tougher, far more talented blues musicians. Is Conan another failed musician that turned to comedy out of disgust, and now his break from straight-laced network format has given him an outlet to show his true colors? That question is never addressed, but still, the self-loathing on display in “Conan O’Brien Can’t Stop” is mind-blowing.

Flender’s fly-on-the-wall approach to Conan’s backstage scenes yields painfully hilarious results. At times, Conan’s behavior reaches Charles Foster Kane levels of petulance and self-involvement. In a “This is Spinal Tap”-like outburst, he barks at a sweet-natured assistant for ordering “buttered fish instead of grilled fish.” He’s equally ill-at-ease with sparse audiences (“I guess no one lives here,” he says of Eugene, Oregon, when he discovers that fans aren’t storming his hotel) as he is with fawning meet-and-greets. When he’s asked to do a comedy show at the uber-hip Bonnaroo festival in Tennessee—an honor never bestowed to any other prime time television comic—he balks at the mud and the anything-goes mentality. A request for him to simply announce a soul band proves to be too tall an order—“No one thinks about burning me out,” he whines. And most shockingly of all, he compares himself, in dead earnest, to Anne Frank.

What makes Conan’s misery so maddening to watch is that he is most likely the luckiest failure in show-biz history. Comics well-known and obscure have crashed and burned on TV, but few of them met with legions of supporters cursing out the network. Conan’s fans are younger, more collegiate, more snidely absurdist than Leno’s or even Letterman’s; they consistently eat up his “How did I get this show, I’m such a loser” act because it mirrors their own insecurities, and it’s more gritty, more real, than the polished ass-kissing Leno resorts to. And the more jaded Conan gets, the more his fan base touts him as the hippest comic on television. It remains to be seen whether that vital demographic will applaud Conan for his bravery, at allowing a film crew to document his ugliest period, or whether it will feel rebuffed by his insatiability.

Wisely, Flender doesn’t structure “Conan O’Brien Can’t Stop” as an attack on the chutzpah of past-their-prime celebrities. O’Brien’s dolefulness and fear about his newfound role as Burnt-Out Hipster Comic is, in the end, rather poignant. It’s as if being glorified by the young confirms his regression, and it’s fascinating to watch this family man, on this non-stop, raucous tour, gradually learning the limits of middle age. “Conan O’Brien Can’t Stop” consistently challenges our shallow, removed viewpoint of the talk show host as mere grinning, debonair prankster.

One minor gripe: O’Brien’s able sidekick Andy Richter is once again pushed into the background. Wearing square, buttoned down shirts that nearly choke him, his crooked, Jack-O-Lantern frown permanently affixed, Richter, his every sardonic quip ignored, looks ready to blow at any point; he really deserves his own documentary.