Early on in the process of developing Coco, the upcoming animated project inspired by the Día de Muertos, Pixar’s artists had to ask themselves a crucial question: how does one animate a skeleton? It seems, at first, like a truly simple question. But knowing that they’d have to populate the Land of the Dead with an entire roster of skeleton characters meant the art department that had gone underwater for Finding Nemo and to space with WALL-E, would have to dive deep into uncharted territory.

At a press event at the Emeryville, California studio in August, animator Gini Santos and her colleagues explained just how they set out to flesh out these characters without, well, any flesh. “We’ve never animated skeletons in our films,” she said. “Our jobs as animators is to bring our characters to life, so bringing appeal to a character that has been universally known as a symbol of death is a challenge we really wanted to take on.”

This was particularly important when designing one of the main characters in the film: Hector. Voiced by Gael García Bernal, Hector is a trickster in the Land of the Dead who wishes to head to the Land of the Living and hopes to recruit young Miguel to do so. The loose-limbed singer is a perfect example of how the Pixar team played with clothing to make these skeletons come alive. With his raggedy pants and open vest, Hector’s design looks quite simple and lends itself to the kind of visual humor that has always made the Emeryville studio such a hit with audiences and critics. By being able to see his ribcage, not to mention see the frayed hat he has on his head, audiences immediately get an idea of the scrawny and scrappy look of this most playful of Coco‘s characters. Add in the fact that a mere moment of shock can send his eyes tumbling down his skull and onto his mouth, and you see quite clearly how the very limitations of an authentic skeleton actually pushed animators to have fun with what they had.

Soon, the simple questions led to other, more complicated ones: do these skeletons wear clothing? If so, how does it fit? If all skeletons are roughly the same size, how do you create a sense of variety? Do they grow eyebrows? How about hair? Do they wear wigs? How about makeup? Do they have tongues? Lips?

Answering these queries meant creating a specific set of rules that would guide how the many characters young Miguel encounters in the Land of the Dead would be designed and animated. Thus, while the Coco team decided to forgo putting tongues on their skeletons, they decided they couldn’t do very well without eyes. And while you’ll definitely see some characters with hair, there won’t be any eyebrows in sight – the eye sockets, in fact, came to play the role those expressive facial features would have anyway. Hearing them discuss these choices shows a keen desire to find the right balance between expressivity and authenticity.

In that sense, what audiences will get to see in Coco is a departure from how things are usually done at Pixar. The motto of “staying true to the material” had to be bent in specific ways. The studio who aimed for photorealism in The Good Dinosaur, and who adhered to the constraints of space toys in Toy Story had to find ways of breaking their own rules if they wanted to make skeletons not only appealing to kids but also representative of Día de Muertos, the main inspiration for the film.

Hector concept art by Daniela Strijleva for ‘Coco.’ Courtesy of Disney-Pixar.

This pushed the designers and animators at the famed studio to keep director Lee Ulrich’s dictum to “embrace the skeleton” in mind. Only, of course, they kept finding ways of softening and changing what that meant. After all, anyone who’s taken a biology course or visited a Natural History museum can tell you bones by themselves can be terrifying.

This is where things like clothing and face painting, a nod to the Día de Muertos style, helped the studio differentiate the 80 skeletons they had to create. In case you’re wondering, each of those skeletons had 127 bones in them, meaning this film includes over 10,000 bones that each had to be painted and shaded. Never ones to shy away from a challenge, the Pixar team not only created software that helped them streamline that process but came up with ways of helping distinguish older skeletons from younger ones. Since they didn’t have wrinkles to work with, animators and designers overlaid different types of patterns in the bones themselves to have the same effect. That’s why older skeletons in Coco (like Mama Imelda) look more weathered than the younger ones (like Hector) — just another example of how a design challenge helped in turn create more inventive artistic choices pop.

Ultimately, what audiences will get to see in Coco is the result of a lot of talented people asking the age-old question: how does one make skeletons interesting but not creepy? Unsurprisingly, part of the answer was, “Hire Gael to voice one.”

Coco already opened in Mexican theaters and hits U.S. cinemas on November 22, 2017.