Improvisational comedy can make some people uncomfortable. It’s hard to pinpoint exactly what it is — maybe it’s the playfulness and lack of shame on the part of the performers. Maybe people who don’t like it are just jealous of the performers’ fearlessness. What is clear once you spend time around a group of improvisers, however, is that the best groups have a sense of family, support and shared mission that you don’t often find among groups of adults.

That familial (if sometimes dysfunctional) dynamic of encouragement and sacrifice makes for a solid backdrop for writer-director Mike Birbiglia to explore what happens when individual ambitions and latent jealousy can poison a group.

"Don’t Think Twice," which made its world premiere at South by Southwest at the Paramount Theatre starts with expository slides and voiceovers that explain the history of improvisation and the main tenants of the art. To wit: 1) Say ‘yes.’ 2) It’s all about the group. 3) Don’t think.

Birbiglia, whose 2012 directorial debut ‘Sleepwalk with Me,’ also explored with vulnerability the act of creating art, plays Miles, a 36 year-old approaching middle age with very few options. He created the Commune (a spot-on name for a NYC improve troupe) that has built a local following and graduated some talent to "Weekend Live," an obvious stand-in for "Saturday Night Live," eccentric and intimidating executive producer and all.

But despite forming the troupe and serving as the instructor at the Commune, Miles can’t seem to catch his break. He had an audition for "Weekend Live" years ago, but his anxieties got the best of him. Or so he says.

Miles makeshift family is rounded out by the nebbish, self-effacing Bill (Chris Gethard), the quirky and creative Allison (Kate Micucci), spoiled pot-head Lindsay, who still lives with her parents (Tami Sagher) and the talented, charismatic and achingly cute couple of Jack (Keegan Michael-Key) and Samantha (Gillian Jacobs).

The film’s quick edits capture the clever and snappy repartee shared by the group, most of whom live together in a college dorm-style apartment, and the roving camera realistically delivers the feel of being at an intimate improve show. But the light-heartedness of lives spent feeding their creative jones while working horrible day jobs has recently been overshadowed by the looming specter of the loss of their performance space.

Adding to the tension is the fact that Jack lands a gig with "Weekend Live," a change in his status that splinters the group and strains Jack’s relationship with Samantha, a performer of equal if not greater talent who seems content to toil for her art outside of the limelight. The film is at its best when it digs into the growing rift between Jack and Samantha. Key brings ambition and boyish charm to a character torn between the life he’s been living and the brighter future that might light ahead, and you can’t take your eyes off Jacobs, as she wanders from charmingly goofy and sprightly, all big, shifting eyes and loose movements, to troubled and introspective. She has an ability to wear her internal feelings plainly on her face while still remaining some of a mystery.

Birbiglia brings a slow-building sadness to Miles, a man approaching middle age but still sleeping with unwitting students, but there is just enough self-awareness to keep the character from straying into obnoxious self-pity. Not all of the characters have the same depth as its three central figures, and the movie attempts to accomplish a lot in its short 90-minute running time. The character’s backstories get fleshed out in short order during the film’s climax, and while that scene may feel a bit contrived, it wholly captures the spirit of the movie and the underlying questions it poses: What happens when the group isn’t the most important thing? Can you simultaneously have everyone else’s back while looking out for yourself? When is it ok to go your own way?