“Best Worst Movie,” a funny-sad documentary about the 1990 horror movie disaster “Troll 2,” tries to pin down the alchemy that transports a film from reject bin to cult favorite. When that goal proves elusive, the director, Michael Paul Stephenson, settles for one closer to home: a touching and at times uncomfortable portrait of people making peace with an unwanted past.

Perhaps none more so than the director himself. A freckled 10-year-old when he starred in “Troll 2,” Mr. Stephenson views the role as the nail in the coffin of his acting career. One co-star refuses to put the movie on her résumé (“I just want it to go away”), while another admits to arriving on the set courtesy of a day-release program from the local mental hospital.

Ranging from hilarious to troublingly intrusive, these encounters reveal a production doomed by ineptitude and the fractured English of its Italian director, Claudio Fragasso. “They know nothing,” Mr. Fragasso grumbles at a sold-out Manhattan revival screening, deeply hurt by the audience’s laughter.

Pained in another way is George Hardy, the father in “Troll 2” and this film’s genial anchor. An Alabama dentist overflowing with folksy bonhomie, Dr. Hardy has so fully embraced his belated celebrity that the discovery of an adulation gap prompts a rare moment of mean-spiritedness.