Comedy is fun -- isn't it?

Conflict emerges in a group of improvisational comics in Don't Think Twice.

Don't Think Twice introduces us to a group of improvisational comedians trying to make it in the highly competitive world of New York-based show business.

Comedy may aim for laughs, but as a business, it's not all yucks. That means we shouldn't be surprised that Don't Think Twice contains some of the year's more painful moments as it skillfully assess success, failure and the hairline difference between the two.

Writer/director Mike Birbiglia, who also appears in the movie, tells the story of The Commune, men and women comics who share a New York City apartment. They're one big happy family -- until, of course, they're not.

Group solidarity runs into trouble when The Commune faces the loss of its performance space. On top of that, troupe members Jack (Keegan-Michael Key) and his girlfriend Samantha (Gillian Jacobs) have been invited to audition for Weekend Live, a big-time comedy show that looks a lot like Saturday Night Live.

Jack's sudden rise to recognition, throws the rest of the group into turmoil. He promises to help the others get auditions or writing jobs, but we know that it's probably an empty pledge. Nothing like a splash of success to undermine a one-for-all spirit.

And for every upward arc, a corresponding downside lurks. Bill (Chris Gerhard), for example, has been working at comedy for a while, and isn't convinced that he'll ever have a breakthrough moment. He's also dealing with a disapproving father, who has been diagnosed with a serious illness.

Look, one of the saddest things in life involves watching people who keep striving long after their expiration date has passed. And some of these characters are right on the cusp of such failure.

To the extent that The Commune has a leader, the job falls to Birbiglia's Miles. Miles once auditioned for Weekend Live, but didn't make the cut. In addition to his work with The Commune, Miles teaches improv. He tries to convince himself that his approach involves a purity that he couldn't maintain if he actually were to get a shot at the world's best-known comedy TV show.

One of the troupe's members winds up delivering a piercing rebuke to Miles, who eventually reunites with an old high school classmate (Maggie Kemper) with whom he'd like to begin a relationship.

It's easy to be dismissive about the characters in Don't Think Twice. Who in his or her right mind really believes he or she can make it in the cut-throat world of comedy? And don't we have bigger problems to worry about, anyway?

We do, but at its best, Don't Think Twice makes us feel for those who must abandon long-held dreams, a phenomenon not unknown outside the world of comedy. It's difficult for everyone to reach the point at which youthful hopes begin to fade.

So credit a canny Birbiglia -- a comic -- with knowing the milieu he's depicting and for doing it in ways that never become such an in-group exercise that we lose touch with the characters.

Don't Think Twice may not be a momentous movie, but it's perceptive and honest enough to demand what the best comedies require: Occasionally, it wants to be taken seriously.

A comic hones his stand-up

A MONOLOGUE BECOMES A MOVIE

If you have any desire to try your hand at stand-up comedy, Sleepwalk with Me could give you major second thoughts. Based on the experiences of comic Mike Birbiglia, the movie tells the story of how a comic named Matt Pandamiglio (played by Birbiglia) hones his chops at a variety of low-rent locations.

Birbiglia, who shares directing credits with Seth Barish, narrates this story of comic aspiration, adapted from one-man show he performed in 2008. Although I didn't find the stand-up routines all that funny, the comic's take on his relationship with Abby (Lauren Ambrose), his live-in girlfriend, is well-observed.

Matt and Abby have been together for eight years. She's ready to marry. He's not. Enough said.

About the title? It turns out that Matt is a sleepwalker who acts out the wild scenarios of his dreams while still asleep, a problem that gives the movie its bizarre climax.

Matt's march toward success begins when he receives a bit of advice from comic Marc Maron, who tells him he'd do well to personalize his act. Maron's suggestion stems from an off-hand remark made by Matt, who says he doesn't want to get married until he's sure that nothing else good can happen in his life. Use that, says Maron.

Birbiglia winds up being a likable enough presence to keep us involved, and Ambrose -- familiar from TV's Six Feet Under -- shines as a woman who ignores more than a few signals about Matt's intentions.

The movie's script was written by Birbiglia, his brother Joe, Ira Glass -- of PBS's This American Life -- and director Barish. The screenplay has Matt talking directly to the camera when he needs to elicit sympathy, a gimmick that probably shouldn't work, but does.

A COMEDY THAT'S NOT TO BE BELIEVED

Neither Jesse Eisenberg nor Melissa Leo can save Why Stop This?, a fatally mixed-up comedy about a brilliant high school pianist who's trying to get his drug-addicted mother into rehab. An early picture contrivance has Eisenberg's Eli and Leo's Penny searching for cocaine so that her urine will test "dirty." The uninsured Penny, who has been clean for three days, is told that the only way she'll qualify for treatment is to fail a urine test. Mother and son contact Sprinkles (Tracy Morgan) and his partner Black (Isiah Whitlock Jr.), drug dealers who, alas, are in need of re-stocking. All four set out to score drugs from a bigger dealer (Paul Calderone). Eli, who on this very day is supposed to audition for a scholarship to a prestigious music school, wants his mother to get straight so that she can take care of his younger half-sister (Emma Rayne Lyle) when he leaves home. Eisenberg, who turns 29 in October, is too old to be playing a high echooler, but he manages a few laughs in a comedy built around escalating desperation. Morgan fares better in the comedy department, and Leo looks appropriately bedraggled. But what is this? A coming-of-age comedy? A comedy about the way illegal drug use creates colliding class contacts? Or a half-serious look at the problems caused by a good-hearted but negligent mother? Whatever it is, Why Stop Now? certainly didn't need scenes in which Eli's high school classmates dress up as Revolutionary War re-enactors. Huh?