If there were ever a man lucky enough to have found his true calling in life, it's the subject of Dave LaMattina and Chad N. Walker's affecting documentary. Profiling the unseen puppeteer who for some 45 years has inhabited the feathered, eight-foot creature that long personified Sesame StreetI Am Big Bird: The Caroll Spinney Story shines a much-deserved spotlight on this unheralded artist.

The now octogenarian Spinney reveals himself to be much like the character he portrays: a sunny optimist with a childlike nature, who clearly takes great delight in performing. Of course, that's probably not all of what he is, as demonstrated by the fact that he also plays the diametrically opposite Oscar the Grouch.

The film relates the story of his life and career with a plethora of enlightening and entertaining anecdotes. Although his mother lovingly supported his fascination with puppets as a child, his emotionally volatile father was far less encouraging. Bullied at school because of his obsession, as well as his name, Spinney joined the Air Force at nineteen and spent four years in the military.

After an initial stint working for Bozo the Clown, he attracted the attention ofJim Henson after delivering a mishap-plagued performance at a puppet festival. The Muppets creator offered him a job anyway, telling him, "I liked what you were trying to do."

His early years working with Henson weren't immediately successful. He had trouble fitting in professionally, and his marriage to a woman embarrassed by his career ended in divorce. He was on the verge of quitting when he literally and figuratively found his way into the character that he continues to portray to this day.

Happily, things got much better from there. He met Debra, who would become his second wife and the love of his life, and his character became an international sensation. He traveled to China to appear on a television special with Bob Hope — a decades-later reunion with a young girl who appeared on the show constitutes one of the film's more contrived elments — and even starred in his own feature film, 1985's Follow That Bird.

He was approached by NASA in 1986 to fly aboard the space shuttle Challenger to promote interest among young children is space exploration. After some initial hesitation, he agreed, only to be later informed that his Big Bird costume wouldn't fit onboard. It was a rejection that ultimately saved his life.

He formed a deep friendship with Henson that lasted until his mentor's untimely death at the age of 53. The footage of him as Big Bird delivering a sorrowful rendition of "Bein' Green" at Henson's memorial is one of the film's most powerfully emotional moments.

There's also fascinating, behind-the-scenes footage that details the arduous physical demands of playing the character, which involves painfully holding his arm upright — it controls the puppet's head — for long stretches at a time. Interviews with such key figures as Frank Oz and the late Jane Hensonprovide further informational context.

Other interesting segments involve his hand-picked successor, Matt Vogel, who has been patiently waiting for nearly two decades for Spinney to retire; the character's diminishing popularity in favor of Elmo when Sesame Street began skewing younger; and the amusing brouhaha that ensued after Mitt Romneydeclared "I love Big Bird," even while vowing to end funding for public television.

The film does get a bit sentimental and treacly at times, but it's a forgivable offense considering the subject matter. Even for adults who've long since moved on to other things, it's somehow comforting to know that the man inside the bird suit is just as lovable as the character he portrays.