Our Idiot Brother 

The title character of Our Idiot Brother isn’t an idiot. He just prefers to live his life as if everyone were as guileless as he is, giving people the benefit of the doubt and hoping they’ll “rise to the occasion.” Hence the opening scene, in which organic farmer Ned (Paul Rudd) lands himself in jail by selling weed to a cop. The officer is in uniform, which does give our hero a moment’s pause. But the boy in blue says he really needs some stress relief, and Ned can’t not help a brother out.

In short, Ned is a “wise fool,” one of those perennial comic characters who exist (1) to get laughs and (2) to make audiences wonder if following social conventions really makes them winners in life or just boring and unhappy. The archetype predates movies by many centuries; Molière would have done a lot with the premise of Our Idiot Brother. For one thing, he would have made it funnier.

Directed by Jesse Peretz from a screenplay by his sister, Evgenia Peretz, and David Schisgall, this comedy offers more indie-style food for thought than, say, Dumb and Dumber, but also far fewer laughs. As a character study, it’s worth a look, mainly for Rudd’s likable performance as a man-child loose in a mean city. But it’s hard to get around the fact that its funniest moments are the outtakes that play during the end credits.

As a comedy, Our Idiot Brother never quite finds its rhythm, perhaps because the script is overloaded with underdeveloped supporting characters and subplots. The siblings who dub Ned their “idiot brother” are three: Liz (Emily Mortimer), a preachy, yuppie stay-at-home mom; Miranda (Elizabeth Banks), a single, stressed-out Vanity Fair reporter; and Natalie (Zooey Deschanel), a mooneyed boho who’s trying to convince her girlfriend (Rashida Jones) she’s ready to settle down when she clearly isn’t. The other two sisters have significant others, too: Steve Coogan is Liz’s husband, and Adam Scott is Miranda’s friend-without-benefits.

That’s a strong cast, and enough setups for several romantic comedies. Place a naïf like Ned in these three Manhattan households full of lies and compromises — released from the clink, he crashes with each sister in turn — and the results should be explosive.

Instead, Our Idiot Brother plays like someone stuck Candide at the center of a middling episode of “Sex and the City.” The sisters and their problems seldom rise above stereotypes, which bog down the film when it needs comic momentum. The subplots in which Ned introduces Liz’s sheltered kid to the joys of YouTube and karate, has a well-worn, sitcom feel; and some would-be hilarious sequences, such as one where Natalie experiments with a cult, fall flat. Rudd’s scenes with Banks have the most potential, making one wish Miranda had tolerated her idiot brother long enough for the writers to bring this plot to a more organic, and amusing, conclusion.

We’ve seen a lot of recent comedies focused on manic wise fools, from the stunted slackers in Step Brothers to the motormouth optimist in Happy-Go-Lucky. Rudd gives his bearded hippie character more of a low-key, expect-the-best-but-deal-with-the-worst vibe, and he seems like he’d be genuinely fun to hang out with.

But the best of these comedies give the “fool” a genuine foil: a hardened cynic who isn’t transparently evil or easily mellowed. Without a fleshed-out character who provides a viable alternative to Ned’s idealism, Our Idiot Brother lacks the friction that generates great comedy. It’s more like a feature- film vehicle for a sketch-comedy character — and even Ned could tell you such promising projects seldom rise to the occasion.