From the 43rd floor of the Park Hyatt hotel in downtown Tokyo, the sky looks clear enough to swim in. Outside, the view stretches on past Shinjuku’s skyscraper district, the Imperial Palace, the glittering towers of Ginza, and on towards Tokyo Bay and the horizon. Inside, the air is cool, the lighting subtle, the furnishings light cream and bitter chocolate.

It was here that Bill Murray and Scarlett Johansson sought comfort in one another’s company in Sofia Coppola’s Lost in Translation – which means to film-lovers, they go hand in hand with culture-clash and jet-lag. In that respect, for the launch of Walt Disney Animation Studios’ 54th film, there could hardly be a less appropriate venue.

In Big Hero 6, cultures don’t clash, they compound. The film is a loose adaptation of a long-defunct Marvel Comics superhero series, but it’s Disney down to its marrow. It takes place in a mashed-up metropolis called San Fransokyo – think of a happy Blade Runner – where Telegraph Hill is topped with a seven-story pagoda, and the steep rows of clapboard houses are lined with sakura in full blossom.

Pictured in concept art, the high-tech city of San Fransokyo from Big Hero 6 Credit: Disney/Disney

There are robots and car chases and portals to alternate dimensions and flying sequences that treat skyscrapers like slalom poles. The only song is a gearing-up anthem by the Chicago pop-punk band Fall Out Boy. In short, it isn’t Frozen 2.

Team Disney launched Big Hero 6 at the Tokyo International Film Festival last week, where it became clear that one of its characters – the living embodiment of its blend of eastern and western pop cultures – was destined for global stardom. He’s Baymax, an inflatable robotic nurse, and he’s Disney’s most straightforwardly adorable character since Robin Williams’ Genie in Aladdin.

In the film, Baymax’s inventor is Tadashi Hamada, an engineering student who perishes in a suspicious fire at San Fransokyo Tech one night, shortly after his younger brother Hiro is accepted into the faculty.

Heartbroken, Hiro falls into a depressive stupor, but Baymax, who’s programmed to make people feel better, draws him back out of his shell.

In reality, Baymax’s inventors are Don Hall and Chris Williams, the co-directors of Big Hero 6, who even now, with the elevated perspective that a 43rd-floor altitude brings, don’t seem fully aware of the sheer, heart-bursting adorableness of their creation. On the film’s UK release next January, Baymax is going to be huge in the way only a 10ft-tall inflatable robot can be.

It was while he was finishing work on Winnie the Pooh in 2011 that Hall suggested to John Lasseter, the director of Toy Story, co-founder of Pixar and, since 2006, Disney’s chief creative officer, that a Disney version of a Marvel superhero story might be fun. Two years previously, Disney had acquired Marvel Entertainment for $4.24 billion, and the deal entailed not only the rights to Iron Man, Thor and the other A-list characters with established fanbases, but also the thousands of others stashed in the Marvel vault.

Lasseter gave Hall the go-ahead to rummage, and he came back with Big Hero 6, a series from the Nineties about a sextet of Tokyo-based superheroes, led by an X-Men-style mutant called Silver Samurai. In the original book, Baymax was a shape-shifting golem who could morph into a dragon and a robot for battle.

“It was the opposite of famous,” says Hall, a pink-cheeked, floppy-haired Iowan who arrived at Disney in 1995 to work on Tarzan.

“I’d never heard of it, and I was a big comic-book nerd. I liked the title – I thought it sounded cool – and a Japanese superhero team, well, that’s cool too. Then I read the comics, and the tone was light, and I thought OK, we can do something with this.”

From that, Hall extrapolated the story of a 14-year-old genius who loses his brother and is then restored back to emotional health by his brother’s invention. Fresh as he may look, Baymax falls into the Disney tradition of elder-sibling surrogates: Pumbaa and Timon, Thumper, Baloo, Timothy Q. Mouse, Jiminy Cricket.

The existing version of the character, a giant marauding dragon/mecha, didn’t seem quite right for the task, so Hall and Williams redesigned him from the ground up. (Marvel took a hands-off approach to the property’s Disneyfication, but two executives, Joe Quesada and Jeph Loeb, sat in on work-in-progress screenings.) The directors visited the Robotics Institute at Carnegie Mellon University in Pittsburgh, Philadelphia, where they were both immediately taken with the department’s ‘soft robots’, whose metal exoskeletons were covered in inflatable vinyl.

“Our mandate was to do something nobody had ever seen before, and I was hooked right off the bat,” he said. “ I just thought, ‘We’ve found a huggable robot.’ Everything about Baymax’s character, personality and design stemmed from that trip.”

Credit: Disney/Disney,

Encouraged by Lasseter, Hall and Williams then flew to Japan to look for further clues to Baymax’s personality. “We’ve both been inspired by Japanese animation since we were very young,” says Williams, a lean Missourian with a goatee and ruffled hair who joined Disney as an intern in 1994 and whose first film with the studio was Mulan.

“When I studied animation at college, there were these things called Hayao Miyazaki movies which would get passed around on VHS tapes, and they were just mind-blowing. I was always struck by how dynamically staged the action scenes were, but there’s also a sentimentality and a stillness that we wanted to capture.”

“During our search, we noticed that the more realistic a robot looks, the creepier it looks,” adds Hall, “so that fed into the thinking that Baymax had to be simple.”

During a visit to a Shinto shrine, Hall noticed that the copper suzu bell above the altar seemed to be smiling at him – “it had such a peaceful, pleasant expression,” he says – and he realised he had found Baymax’s face. To find his walk, the directors and their animators looked for cute movements in nature: after consulting much source footage, they decided on a toddler with a full nappy was the cutest. Baymax’s cuddliness was partly inspired by Miyazaki’s 1988 masterpiece My Neighbour Totoro, in which a large, fluffy forest creature helps two girls, Satsuki and Mei, cope with the absence of their mother, who is convalescing in a country hospital.

In fact, the film’s Japanese publicity campaign sidelines the heroism entirely, and focuses on the relationship between boy and ‘bot. (Despite the title’s syntactic tumble, ‘Big Hero 6’ isn’t a translation: in Japan, the film is simply called Baymax.) The trailer even opens with a shot of umbrellas in the rain: a respectful nod towards the most famous sequence in My Neighbour Totoro, in which the creature stands with Satsuki and Mei at a bus-stop during a downpour.

At a festival seminar in Roppongi’s Ex Theatre the day after the Big Hero 6 premiere, Lasseter, dressed in an orange and cream Hawaiian shirt patterned with Baymax’s face, dissected the bus-stop scene shot by shot, calling it “one of the most amazing sequences ever put on film in history”.

“It’s the opposite of Hollywood filmmaking, where the attitude is always ‘I’m going for popcorn, you’re boring me’,” he said. “Miyazaki celebrates the quiet moments in films. In this sequence, there’s nothing happening, but the beautiful, prolonged moments it depicts are so special.”

Credit: Disney

Accordingly, Big Hero 6 contains similar, though briefer, passages of calm. After Hiro builds Baymax rocket boots, and the pair go flying through the streets of San Fransokyo, they soar up above the clouds and sit on top of a hot-air balloon, watching the sun set and twisting their feet in the breeze.

“John. That was John Lasseter,” says Hall, as soon as the words “Whose idea was it for the feet….” leave my mouth.

“The sequence was already animated with Hiro twisting his feet, and it was beautiful, and then John looked at it and said, ‘Do you know what would be really cute? If Baymax looked down at Hiro’s feet and started twisting his too.’ So we went back to reanimate it, and it’s one of my favourite moments of the film.”

Hall and Williams both talk about their boss with a zeal that flits between puppyish and cult-like, although given their histories at Disney Animation, it’s understandable. Both witnessed firsthand the studio’s agonising decline in the late Nineties and early 2000s, when Beauty and the Beast and The Lion King gave way to the likes of Chicken Little and Brother Bear.

“All through that time we were looking at the incredible things Pixar were doing and saying, ‘Who’s going to be our John Lasseter?’” remembers Williams. In January 2006, Disney employees found out, when they were summoned to a sound stage on the studio’s Burbank lot to meet their new C.C.O.

“Out on the stage walks John Lasseter,” Williams continues, “and boy, the ovation and cheers. We knew it was going to be a completely fresh start.”

One of Lasseter’s first acts was to replace the existing commissioning system at Disney, in which a panel of ‘creative executives’ handed down films to directors, with the one he had initiated at Pixar, where directors pitched their own ideas directly to him. Another was to insist that directors build their film’s world before refining its story, allowing that research to inform character and plot.

San Fransokyo was the result of hundreds of preparatory sketches made by the film’s production designer Paul A. Felix and art designer Scott Watanabe – of things as dull as manhole covers, vans and vending machines, trying to locate the differences between eastern and western versions of both. (Japanese journalists have been particularly impressed by the crates of empty beer and sake bottles stacked in the city’s alleyways.)

As a result, San Fransokyo feels plausible and complete: not just like somewhere you’d love to visit, but somewhere you could – as real as Agrabah, the Pride Lands or Arendelle. Forty-three stories above the ground, in a cloud of jet-lag, with shrine bells smiling 700 feet beneath you, the fantasy doesn’t seem so far away.

Big Hero 6 is released in the UK on January 30