If comedy is tragedy plus time, improv is the purest expression of its instability, since every moment turns on the desperation of finding the way to a joke. "Don't Think Twice," Mike Birbiglia's sharply directed follow-up to his acclaimed debut "Sleepwalk With Me," captures the essence of that communal practice through a tight-nit gang of New York performers struggling together to keep their art alive. A delicately wrought ensemble piece with first-rate turns by Gillian Jacobs, Keegan-Michael Key, and Birbiglia himself, "Don't Think Twice" scrutinizes its playful setting and finds an ideal entry point for exploring creative desperation.
"It's all about the group," announces one of several title cards in the movie's opening sequence, which unfolds like a mini-documentary on improv history. (The approach suggests the fingerprints of "This American Life" creator Ira Glass, who served as a producer, as he did on Birbiglia's previous film.) Over the next 90 minutes, the group's bonds are continually tested, with the utopian energy of the troupe threatened by several developments.
Their collective, aptly dubbed The Commune — though it comes across as a thinly veiled version of New York's Upright Citizens Brigade — initially seem perfectly content to amuse a small audience and teach classes each week. With time, however, various anxieties bubble to the surface: More than one participant jockeys for a spot on "Weekend Live," an obvious riff on "Saturday Night Live" that represents the high water mark of achievement for the restless performers even as they cynically dismiss it as subpar. "The great paradox of 'Weekend Update,'" says Miles (Birbiglia), the late-thirties founder of the Commune, "is that it never was great."
Yet even he grows envious when one of his former disciples lands the plumb gig, and joins the chorus of voices hoping to land a favor from the newly minted star. Meanwhile, Miles also copes with the mounting sense that he's outgrown the profession, and the claustrophobic apartment space that it affords him.
The others have hangups of their own: energetic Jack (Key, showing greater dramatic range than anything in the "Key & Peele" sketches for which he's best known) can't suppress his tendency toward showboating whenever a "Weekend Live" recruiter attends one of their shows; his girlfriend, fellow performer Samantha (Gillian Jacobs, stellar), tries to mirror his enthusiasm but can't shake the perception that she's happy to stay put. Allison (Kate Micucci) harbors separate aspirations of writing a comic book; Lindsay (Tami Sagher) grapples with the guilt of her sheltered upbringing. Bill (Chris Gethard) seems mostly satisfied, but copes with the distracting news of his father's terminal illness. Birbiglia captures the six-person cast with Altman-like finesse, dipping in and out of their casual conversations to highlight the hive-mind dictating their lifestyle. As Samantha observes early on, improv demands that participants "agree with the reality your partner creates."
"Don't Think Twice" doesn't give each character equal screen time, and some stories feel more developed than others. But each plot has its own compelling hook, and they dovetail nicely into a satisfying balance of humor and melancholic yearning. It's a particularly tricky balance for a movie about the outer rim of the entertainment industry, and Birbiglia even manages to slip in a few big cameos (Ben Stiller gets a great scene) without ruining the narrative. Instead, "Don't Think Twice" maintains a striking realism throughout (cinematographer Joe Anderson's roaming camera is especially effective at exploring the improv stage) that forms an impressive contrast to the performative tendencies of its subjects. Even as they try to remain cordial, the Commune's interdependency makes them vulnerable to sudden changes. "Without improv," one of them says, "I'm kind of just a loser."
No character faces down that possibility more than Samantha, whose weak self-esteem turns her uneven stage performances into a series of public therapy sessions. Jacobs portrays the troubled woman with jittery energy and furtive glances that marks the best statement on the irony of the comedy profession this side of "Louie." She's matched only by Birbiglia, who plays Miles as an aging hipster confronting his hand-to-mouth lifestyle without overstating his neuroses.
Ultimately, "Don't Think Twice" caves to formula, in a climactic showdown where which everyone's major hangups collide at once. The tidy epilogue seems out of place in a story about messy performances. Even then, however, the movie retains its philosophical approach to a craft generally regarded in more simplistic terms. The imperfections of "Don't Think Twice" are fitting for a movie about artistic expression that's never quite finished.