In director Henry Koster’s beautifully batty comedy Harvey (1950) James Stewart plays Elwood P. Dowd, a pleasant mild-mannered alcoholic who walks around in a bubble of impenetrable happiness.

Elwood behaves like an inhumanely nice person. He has, arguably, one vice: his best pal is a seven foot invisible rabbit, but no matter ’bout that. Elwood is so kind, so affable, so nonjudgmental, so seemingly ignorant of the scorn from the sneerers around him that he seems, for a long time, stupidly naive, almost to the point of having a kind of moral retardation — or at least an inability to grasp the harsh realities of the world he occupies and the flawed personalities who populate it.

In one crucial scene, however, a few simple lines of dialogue articulate his character’s deep motivations, his raison d’etre, and make it clear that Elwood’s unusually kind behaviour is a conscious choice. Elwood says that his mother used to tell him he could one be one of two things in life: really smart or really pleasant. “For years I was smart, ” he says. “I recommend pleasant.”

Fast forward 61 years and in Our Idiot Brother Paul Rudd, channeling Lebowski-esque mannerisms, all slowwwww summer fruit bowl smiles and chill vibes, plays a reincarnation of Stewart’s character, this time with an emphasis on trust (more on that in a mo) rather than pleasantry — though both in this instance come hand in hand.

In the film’s opening scene Ned sells dope to a uniformed police officer, genuinely believing and feeling sorry for the badged cop when he tells him he’s had a rough week and wants some hooch to relax. Gotcha! Ned promptly lands in the slammer.

It’s the first act we witness of his sheer stupidity — or so we naturally label it, at this stage — and there are many more: Ned asks a total stranger to hold a wad of cash; informs his parole officer he got high; believes his brother-in-law when he says he was naked with a ballerina for professional purposes.

But, just like in Harvey, a fleeting moment arrives that lifts the curtain on Ned’s psyche, briefly and without dramatic accentuation. Ned recounts the story of how he was arrested and explains to a bemused “what’s up with you? why’d you do that?” stranger his core life philosophy: that if you place your trust in other people everybody will ultimately be rewarded.

His excessive trustworthiness in others is a choice, just like Elwood’s.

Director Jesse Peretz is less kind to Rudd’s character than Koster was to Stewart’s. Ned is the victim of the shark bait end of the meathook logic once articulated by Hunter S Thompson: that “in a closed society where everybody’s guilty, the only crime is getting caught. In a world of thieves the only final sin is stupidity.” On those terms Ned is guilty as charged, again and again and again.

The premise Peretz executes with mild-tempered, semi-aloof direction is a good’un — that his protagonist is such a decent bloke he inadvertently upturns the lives of those he holds most dear, turns their existence into chaos.

After Ned is released from the can — he leaves early due to good behaviour, because he’s nice to everybody — he flitters between the homes of his three sisters and mother and inadvertently lands himself into spots of bother. The cause is virtually always the same: he is too honest, too trusting, too ready to talk and share and shoot his mouth off.

Big Lebowski fans will wait for Ned, who is partial to reefers over White Russians, to say something akin to “he peed on my rug, man,” such is his likeness to Jeff Bridge’s iconic knucklehead, but without Lebowski’s angry, angsty streak.

The film itself is vastly different from both Lebowski and Harvey, padded with deadpan quirk and moulded with a homey, personal feel. Rudd’s performance is more than an anchor for the narrative, it’s an engine, a chassis, a foundation, and the supporting characters’ lives and dramas float in and out of his life with low impact until they reach him and his often reluctant response. Rudd is adorable; a departure from his comfortable straight guy shtick. Ned’s buddy-buddy, palsywalsy warmness will be remembered for some time.

As a character study Our Idiot Brother is wonderful. As an ensemble piece about a disconnected family it fares less well but still endears. The dramatic loose strings and left over bits-n-bobs come together a little messily at the end, but the film’s shaggy structure masks its shortcomings, and as soon as Peretz cuts back to Rudd’s hairy face, with that pleasant smile, that sweet kiddish countenance, that Elwood P. Dowd-like wholesomeness, all is right in the world, if only for a moment.

Our Idiot Brother’s Australian theatrical release date: November 3, 2011.