Suffering abounds in Adam Elliot’s dark and deadpan films. The Melbourne animator’s claymation characters overdose and lose testicles or imbibe on an array of poisons; they are assailed by strokes and lightning strikes. These beloved underdogs, the Oscar-winning film-maker says, are studies in human imperfection: “I’ve realised my films are about perceived flaws that often aren’t actually flaws.”

Elliot won his Oscar for the 2003 short film Harvie Krumpet, introducing the world to his surprisingly whimsical style. Global attention followed, and his first feature, 2009’s Mary and Max, starred Toni Collette, voicing a little girl who begins a pen pal friendship with the late Philip Seymour Hoffman’s Max, a New Yorker with Asperger syndrome.

Elliot’s new film Memoir of a Snail – all shot in shades of 1970s brown and set in Melbourne, Perth and Canberra – comes 15 years after his feature debut. It has a typically high corpse count. “I’m really fascinated by peculiar deaths,” he says. “I mean, I shouldn’t laugh, but I love funny deaths.”

His latest heroine, Grace Pudel, a hoarder of ornamental snails traumatised by the early death of her mother, is voiced by Succession star Sarah Snook. Grace’s clay figurine lies disassembled, tucked away in Elliot’s studio here in a former boxing gym in Melbourne’s Docklands. Beside Grace are dozens of characters, each in their own cardboard “coffin”.

The studio lies under the eye of the enormous yet defunct Melbourne Star observation wheel – like a morbid detail in an Elliot story. His celluloid death toll began with his first film, the 1996 student short Uncle, in which an aunt is quickly dispatched by drinking ant poison. Later, in Harvie Krumpet, the eponymous character is blithely unaware of his Tourette’s, his cancerous testicle and his eventual Alzheimer’s, while his friend Wilma overdoses on morphine.

“When I made Uncle, people said, ‘Your stories are so depressing and dark,’ and I couldn’t understand that,” he says. “Somebody wrote on IMDb, ‘Adam Elliot’s films are all the same’,” he laughs. “I thought, ‘Well, they are all the same’; they tend to have sad, tragic endings, the characters tend to die. But why does everything have to be Disney? Why do they have to have these perfect endings?”

Memoir of a Snail is typically twisty. Snook’s character, in a meta touch, is a stop-motion animator making her own film. Alongside her is Kodi Smit-McPhee as her gay twin brother and protector Gilbert. There’s Grace’s father Percy (French star Dominique Pinon) – an “alcoholic, paraplegic, mouth juggler” – and a cameo from Nick Cave, though it’s Jacki Weaver who comes close to stealing the show as Grace’s only true friend: the elderly, toothless Pinky, a former exotic dancer who played ping-pong with Fidel Castro and had sex with the late country crooner John Denver in a helicopter. “Hopefully we won’t be sued,” Elliot says.

In Elliot’s hands, unforeseen death becomes almost comedic relief. Those same hands, he shows me now, shake with a hereditary physiological tremor. The condition, he says, feeds his “wonky” aesthetic and requires other animators to do most of the studio work – seven in the case of this latest film.

He’s also asthmatic, and steroids make his tremor more problematic, while anti-epileptic drugs prescribed at one point left him “foggy and dizzy” – all grist to the empathy mill, he agrees now, for his stories, based in part on the foibles of loved ones as well as things he hears while eavesdropping on public transport.

Making Memoir of a Snail was a decade-long process of soul-searching. “I went through a period of despondency and then depression,” Elliot says, “because Mary and Max was so difficult … to finance and get made.” That film cost $8m but lost money at the box office; in the intervening years, Elliot made one short film, the 2015 work Ernie Biscuit, about a deaf Parisian taxidermist.

In 2017, he sold the home he shared with his partner Dan Doherty – the same “boyfriend Dan” he’d thanked all those years ago in his Oscars speech after just two months of dating. Downsizing to move into the city, Elliot began to reflect on his family’s “mild” hoarding. Elliot’s father, a former circus acrobat and storage unit company owner, died around that time and had “three sheds full of stuff”; his mother, now 82, kept biros and teabags in Ziploc bags. And there was Elliot’s own collection of “knick-knacks, taxidermy, old antiques and bric-a-brac”.

Taxidermy? “I had a piranha, a squirrel, a chicken, an antelope,” he laughs. He deliberately looked for bad taxidermy: “I found a lot of them just in secondhand stores. You know, $5 deformed chickens. I had a tiny, deformed budgie.”

After his father’s death, Elliot began writing Memoir of a Snail’s main character, Grace, as a person who collected excessively. As research, he started watching “exploitative” documentaries about hoarders: “I quickly realised a lot of these extreme hoarders had suffered trauma, and usually they had lost a family member or a child very early on.”

Elliot continues to cross lines and challenge audiences. “I said to someone the other day, ‘Look, if I don’t get a death threat, I’ll be surprised’, because we do lampoon fundamental Christians [in the film],” he says. “There’s a whole sequence … about gay conversion therapy.” Elliot, who came out as gay at the age of 24 “after a backpacking trip to Europe opened my eyes to all and sundry”, has wittily cast the gay actor and comedian Magda Szubanski as the voice of Ruth Appleby, the gay conversion therapy leader.

Was he subjected to such therapy himself? “I wasn’t,” he says. “[But] I’ve got one friend who I can’t name [whose] mother sent him to a psychiatrist to be ‘fixed’, and that was only 20 years ago.” He looks back on his Sunday school teachers from the Uniting church and recalls them as “dodgy”; he has friends, he says, “who were badly abused in the Catholic church – who doesn’t?”

Elliot was later educated at a Christian boys’ school. “We would have religious studies in period six, where we were told God created the universe, and for period seven we’d have science. I’ve always been fascinated by these contradictions. I’ve read the Bible back to back.” By the time he’d left school, Elliot had become a “staunch atheist”.

“We burn a crucifix in this film, so that’s going to upset people,” Elliot muses. “But I think that’s the job of a writer and a director: to push the boundaries.

“One of our lecturers at film school said, ‘If an artist doesn’t push the boundaries, then the art form becomes boring, and when the art form becomes boring, the art form dies’.”

• Memoir of a Snail opens in cinemas across Australia on 17 October, and is showing at BFI London film festival on 10, 12 and 18 October.