Calling all amateur malacologists: With “Memoir of a Snail,” stop-motion director Adam Elliot (an Oscar winner for “Harvie Krumpet”) invites us to study snails of every shape and size, starting with a gastropod-hoarding outcast named Gracie Pudel (pronounced “puddle”), who withdrew from the world after an unhappy childhood in which she was bullied and orphaned and shipped off to Canberra to be raised by a pair of negligent swingers.

Fitting squarely on the shelf of grown-up films about misfit kids, Elliot’s latest — which comes 15 years after Sundance opener “Mary and Max” — finds the Australian auteur deeply committed to his dark and surprisingly moving brand of storytelling. Like Edward Gorey’s, his palette is nearly monochromatic; his characters tend to face the camera, à la Wes Anderson, as if posing for gloomy school photos; and his John Waters-esque humor is irreverent enough to encompass everything from disabilities to weird sexual kinks (including a homeless judge fired for masturbating in court and an adipophile who fattens up his bride with milkshakes and microwave sausages).

Elliot’s characters may be kids, but his audience isn’t meant to be in a film that has poignant things to say about mental health.

“Dad used to say that childhood was like being drunk. Everyone remembers what you did except you,” quotes Gracie (voiced by “Succession” heir Sarah Snook), who can’t quite relate to her alcoholic parent’s point of view. Gracie has crystal-clear memories of her childhood (it wasn’t all that long ago). She adored her beloved twin brother, Gilbert (Kodi Smit-McPhee), and hated the bullies who called her names for having a cleft palate. The more Gracie was mistreated, the more she curled up into her proverbial shell — an idea Elliot illustrates by superimposing a giant gastropod on Gracie in the schoolyard.

Though the stop-motion aspect will undoubtedly get the most attention, “Memoir of a Snail” is foremost a feat of screenwriting — one viewers would do well to take more seriously than Elliot does (his writer-director credit appears scrawled on a toilet lid in a junkyard-set opening-credits sequence). The movie is composed of wall-to-wall narration, as Gracie eloquently (if somewhat naively) describes how she wound up retreating from society. Turns out, her mom was a snail enthusiast, and from a young age, Gracie was drawn to the spiral-shaped creatures.

As life got more difficult, she disappeared into books and surrounded herself with everything snail-related she could find: ceramic figurines, a music box, even novelty condoms. When we meet Gracie, she’s wearing a dingy knit cap with ping-pong-ball eyes on bendy stalks, and standing by the deathbed of her elderly friend Pinky (Jacki Weaver, whose raspy voice perfectly conveys the incorrigibly rebellious spirit of a woman who could never stay married for long). An ex-table dancer with a heart of gold, Pinky’s the first of several characters to kick the bucket in a movie that doesn’t get too sentimental about death or sex — even if adult Gracie’s pet guinea pigs are having a lot more of it than she is.

Gracie agrees to honor Pinky’s dying wish, taking her ashes out to the vegetable garden, where she also liberates the jar full of snails that have kept her company all these years. Over the next 90 minutes, Gracie shares why she came to be so obsessed with the slimy mollusks (who’ve had quite the run in stop-motion animation lately, from “Marcel the Shell With Shoes On” to the snails in last year’s “Chicken Run” sequel). Gilbert and Gracie’s mom was a malacologist, and from a young age, Gracie was drawn to the spiral-shaped creatures. As life gets more difficult, she surrounds herself with everything snail-related she can find: ceramic figurines, a music box, even novelty condoms.

Gracie doesn’t make friends easily, but the bonds she does form leave an impression, starting with her twin brother. Design-wise, she and Gilbert look like “Peanuts” characters as Tim Burton might have drawn them: squatty, roundheaded kids with wiry black hair and dark circles under their rotten-egg eyes. In another movie, they’d be the weirdos — Gilbert is a budding arsonist with depressive tendencies, and Gracie has all kinds of social anxieties — whereas Elliot is drawn to such traits. Here, the adults appear pockmarked and deviant, flaunting their eccentricities in plain view of the kids (one reason you might want to leave your own at home).

After the death of Gilbert and Gracie’s father — who had been a Parisian street performer until a drunk driver rendered him a paraplegic — the kids are split up and sent to foster homes on opposite coasts of Australia. Gracie gets the better deal: Her new folks are nudists, but they leave her alone, whereas Gilbert is raised by a family of holy rollers, who see his pyromania as the devil’s influence. The pleasure of “Memoir” is in the details, and Elliot has a knack for picking unusual ones that are too often excluded from screen stories, but which render his creations more true to life than many live-action characters.

In keeping with “Harvie Krumpet” and “Mary and Max,” the sensibility isn’t so much an acquired taste as a very specific (and potentially limiting) one — and yet, who hasn’t felt ostracized or teased for being different? Elliot celebrates and elevates the things that set people apart, embracing what others might label “ugly” or “awkward” by finding a poetic way to reclaim those traits as strengths. He’s aided by a terrific voice cast (including Nick Cave and Eric Bana in minor but impactful roles) and a tone-setting score from Elena Kats-Chernin.

Elements that might feel frivolous on first mention invariably pay off later, as Elliot brings things around in thoughtful and emotional ways, to the point you forget you’re watching people made of Plasticine. Still, there’s a magic to 100%-CG-free stop-motion, with its cellophane flames and tears made of sexual lubricant. Don’t be surprised if “Memoir” has you shedding real ones in your seat.