In the conspiracy-theory universe, it has been alleged that the televised footage of the 1969 Apollo 11 moon landing was a hoax, staged by no less a cinematic luminary than director Stanley Kubrick, who perfected the art of science fiction with “2001: A Space Odyssey.” That crackpot hypothesis forms the premise of “Moonwalkers,” a would-be gravity-defying comedic romp that is now landing in theaters with all the weight of an earthbound moon rock.

Through a series of misunderstandings, Kidman (Ron Perlman), a CIA operative who has been tasked with bribing Kubrick to take the job, accidentally hands over his suitcase full of cash to an irresponsible British junkie named Leon (Robert Sheehan) whom Kidman has mistaken for the American director. Apparently, the Apollo 11 mission is in trouble, and a fake moon landing is needed to ensure continued NASA funding for the space program.

Leon and his roommate, a mildly disreputable band manager named Jonny (Rupert Grint of “Harry Potter”), have no intention of using the money to actually make a film — that is, until Kidman realizes his mistake, and threatens to kill them if they don’t. Also involved: a violent mobster to whom Jonny owes money (James Cosmo).

There’s little payoff in trying to make sense of the various plot threads. The logic holes in this film are several, and the more you dwell on them, the less fun you will have.

Much of that fun, though paltry, comes from the movie’s amusing evocation of swinging 1960s London. In desperation, Jonny contracts with a caftaned German director of art films named Renatus (Tom Audenaert) to create the fake moon-landing film, which shifts the action to Renatus’s druggy, free-loving commune of hippies, while giving Kidman — who suffers from Vietnam flashbacks — an opportunity to undergo some sexual healing, via the sweet love of a flower child (Erika Sainte) and ingestion of illicit pharmaceuticals.

Neither Grint nor the hoax subplot are compelling enough to hold our attention. Perlman, on the other hand, is a commanding, if peripheral, presence, diverting the focus of the film from silly historical speculation to the tale of a damaged psyche. “Moonwalkers” shoots for the moon, but the only interesting part of the story involves one small step for a man.

R. At the Angelika Pop-Up at Union Market. Contains obscenity, violence, drug use, nudity and sexual and scatological humor.
97 minutes.