Clara (Maggie Gyllenhaal), Frank (Michael Fassbender) and Jon (Domhnall Gleeson) make quirky music as the Soronprfbs in “Frank.” (Magnolia Pictures)

The boho-absurdist lark “Frank” reveals itself like a Russian nesting doll of references, sendups and sly winks aimed squarely at rarified hipster culture, simultaneously puncturing its most pretentious excesses even as it celebrates its ethos of artistic purity.

Perhaps the film’s most subversive act is to bury its lead actor, Michael Fassbender, underneath an enormous fake head — a cartoonish sculptural bubble that bobs over his toned body like an audacious rebuke to everything cinema holds dear. Fassbender, of course, has made a career out of putting his body through all manner of punishment (“Hunger”) and full-frontal exposure (“Shame”). In the process, he has emerged as a dreamboat for the new century, the thinking person’s blue-eyed, rakishly grinning male pin-up.

Well, goodbye to all that, at least for now. As the enigmatic title character of “Frank,” Fassbender turns the tables, playing a man who can’t function unless his face is hidden by an all-enveloping (albeit well-ventilated) papier-mâché carapace. Viewers may miss Fassbender’s gorgeous mug in the movie’s first few minutes, but they’ll soon be captivated — or at least distracted — by his portrayal of a gifted, troubled artist possessed of equal parts eccentric charm and spiky self-involvement.

Our guide into Frank’s world is Jon (Domhnall Gleeson), a ginger-haired would-be songwriter who has stumbled across Frank and his avant-garde pop band, the Soronprfbs: a temperamental theremin player named Clara (Maggie Gyllenhaal), a Velvet Undergroundish drummer (Carla Azar) and bass player (Francois Civil), and a fifth-Beatle-type manager named Don, played with manic wordiness by Scoot McNairy.

When the band’s keyboard player tries to drown himself, Don quickly enlists Jon to join the band. A few days later, the wide-eyed naif finds himself ensconced in a lakeside cottage in Ireland, helping Frank and the group record the album that will finally put them on the musical map. Directed by Irish filmmaker Lenny Abrahamson from a script by Jon Ronson and Peter Straughan, “Frank” is loosely based on Ronson’s encounters with the late British musician Chris Sievey, who in the 1980s became a cult sensation with his character Frank Sidebottom, although there are no reports of Sievey taking his alter ego quite to the extremes suggested here.

Like “Lars and the Real Girl” by way of Nick Hornby and Wes Anderson, “Frank” traces Jon’s adventures into the land of art and fellowship with gentle, joyful sweetness that borders on the precious. Jon tries to get at the root of Frank’s issues, but he, like the audience, must finally accept him as the personification of childlike joy and liberated truth (represented here by people twirling around on the cottage’s lawn or sincere late-night conversations in which he lets Jon know what facial expression he’s using, like “welcoming smile”). As ingratiating and often winsomely amusing as “Frank” is, the Soronprfbs’ cavorting, contorting antics make a condescending burlesque of the creative process: Although Gyllenhaal offers a refreshingly tart relief to Jon’s puppyish eagerness to please and Frank’s mushy opacity, her black-clad femme fatale seems cut from scary-art-lady cloth that the Coen brothers pretty much depleted in “The Big Lebowski.”

Things come into sharper focus during the movie’s final third, when Jon himself leads the ad­ven­ture and Frank’s history and motivations become clearer. As a recessive, withholding character hiding in plain sight, Fassbender’s unconventional star turn in “Frank” winds up being hauntingly transparent. And what started out as a twee, ingratiating indie-music comedy becomes a more complex, even moving meditation on authenticity, self-knowledge and the dubious mythologies that attach to creative genius and mental illness. Beneath those puppet-headed antics, and true to its title, “Frank” is improbably, disarmingly honest.

★ ★ ★

R. At Landmark’s E Street Cinema. Contains profanity and some sexual content. 94 minutes.