It is generally not good critical form to lift a film’s publicity materials when writing about it, but the official logline for Quentin Dupieux’s “Mandibles” is such a masterpiece of the form that it merits quoting, and admiring, in full: “When simple-minded friends Jean-Gab and Manu find a giant fly trapped in the boot of a car, they decide to train it in the hope of making a ton of cash.” As well as a crisp precis of what the film is about — and let it be stressed that this 77-minute prank of a film about no more than that — it’s an ideal litmus test for its potential audience. If you merely think that sounds like the dumbest thing ever, walk on by. If you think that sounds like the dumbest thing ever and you absolutely have to see it, you won’t be remotely disappointed: “Mandibles” is as brazenly and riotously stupid as it sounds, but with a chill, dopey sweetness that makes it stick.
Over eight features, DJ-turned-filmmaker Dupieux has established himself as the preeminent auteur of the one-joke movie, which isn’t the slight it seems: His best work, and “Mandibles” is up there, tends to prove that one is all you need when the joke is both elementally funny and rich in loopy cinematic potential. Last year’s “Deerskin,” with its deft, dark genre-blurring and inspired use of major French stars Jean Dujardin and Adèle Haenel, brought him to the outer brink of the mainstream; “Mandibles” happily spins its wheels there, but it’s a sunnier, scrappier effort all round. If its oddball optimism feels somewhat new for Dupieux, longtime cultists will eventually be rewarded with his more macabre comic instincts too.
In Manu (Grégoire Ludig) and Jean-Gab (David Marsais), meanwhile, he has created an immediately lovable dimwit duo who deserve to carry at least as many adventures as their spiritual transatlantic cousins Bill and Ted. The former is introduced asleep on the beach, wholly cocooned in a pastel-pink sleeping bag that appears to be his permanent home, rolling gently into the surf before someone wakes him. This is as much as we get of his backstory, and as much as we need to know. The promise of €500 makes him take a one-off job that is a nested series of macguffins. He has to steal a car, collect a briefcase, place it in the trunk (not, he is strictly instructed, the back seat) and deliver it to another location on a parched, balmy stretch of French coastline — invitingly shot by the director himself in hot, melted-margarine hues.
So, Manu hotwires a hotwires a rusty yellow wreck, picks up his equally cement-headed bestie Jean-Gab for the ride, and sets out. What can go wrong? In Dupieuxland, pretty much anything, and in the most extravagantly absurd way possible — beginning with that promised giant housefly that our hopeless heroes discover too late in the trunk, taking up every spare inch of it. Lesser men would dump the fly, the car, or both. Jean-Gab is made of more insanely resourceful stuff: He suggests they ditch the courier job, tame and train the obscene insect, and instead make their fortune by using it as a live, bank-robbing drone. Of course Manu agrees: This would be an even shorter film if he didn’t. The pleasure in this brand of farce depends on accepting up as down as sideways.
Assorted scenarios of larceny and mistaken identity ensue, as the boys shack up with a wealthy young vacationer (India Hair) and her friends — including the initially taciturn Agnes, played with wholly surprising, go-for-broke comic verve by the wonderful Adèle Exarchopoulos, who emerges as the closest thing this largely stakes-free romp has to a villain. There’s nothing to spoil here but the gags themselves, which are inevitably funnier seen than described: Exarchopoulos, gamely sending up her signature solemn intensity as a performer, gets several of them, including one exquisitely delayed reaction shot worthy of Madeline Kahn or Catherine O’Hara.
All the while, Dupieux’s skippy, carefree storytelling blithely defies analysis like, well, a fly escaping a swatter. There’s no moral or metaphor to be drawn from these hijinks, though the film’s unexpected humanity is the ace up its sleeve: It’s a testament to the wonderfully synched, spacy performances of Ludig and Marsais that we feel as much for these useless bros, with their dorky secret handshake and genuine care for each other, as one can possibly feel for characters essentially drawn as stick figures with bad hair. Even the fly, perfectly named Dominique, is adorable against all odds: a marvelous feat of puppetry that turns out to have the eager temperament of a family dog, as well as its size. You leave “Mandibles” briefly thinking a trained pet fly mightn’t be a bad idea: Such is the power of Dupieux’s infectious idiocy.