The scariest monster in Stranger Things 3 was almost too gross for Netflix

One of the problems in science fiction is that people don't stay dead.

Stab them in the neck with a pair of scissors or cave their head in with a fire extinguisher and still, they might rise up again in zombie form — or something worse.

“Something worse” was exactly what special effects company Rodeo FX was called on to create when the Duffer brothers (Ross and Matt) hired them on for Stranger Things Season 3.

“They also had wonderful concept art, which made it pretty easy as well,” lead effects artist Nathan Arbuckle tells Inverse.

In “The Flayed,” the fifth episode of the season, Nancy and Jonathan go up against evil journalists Tom Holloway and Bruce Lowe in Hawkins Memorial Hospital. Just when the men seem to have been killed, something horrible happens: They begin to melt. Their bodies lose all structure and are replaced by red squirming masses of blood, bones, and gristle. Worst of all, these hellish slime sacks are autonomous and continue to pursue the teenagers, even combining forces to become one enormous entity and stand on hind legs.

Everything about the creature — concept, movement, texture, sound — is heroically repulsive. So it’s no surprise that creating this monster was a heroic feat as well, but the story of Rodeo FX’s Stranger Things monster and is weirder than you might think.

A gorilla and a crab

“We had to melt people,” says Nathan Arbuckle, conveying the difficulty of the job.

Arbuckle was lead effects artist on Stranger Things Season 3. So more than perhaps anyone else, he was responsible for how the creature looked. He had a vision of what he wanted, bolstered by various references from the Duffer brothers taken from ‘80s movies like Clive Barker's Hellraiser and John Carpenter's The Thing.

Before Arbuckle created anything in visual effects, however, the team needed to be on the same page.

“When we're talking about something that is quite abstract, everybody has his own idea of what it should look like,” says Martin Pelletier, VFX supervisor on the series.

The Duffer brothers had detailed storyboards they shared with Rodeo. Visual effects supervisor Paul Graff (who works for a different company) described the creature as looking like “Frankenstein's dinosaur”.

“The grosser the better.”

But it was difficult to find real-life reference points. One, says Pelletier, was what would remain of a carcass after a pack of wolves had been chewing on it. Another, explains animation supervisor Yvon Jardel, was images of severed arms and bad injuries — the kind of viscera that would be on show if a human body were split open.

To begin with, the trio — along with many other members of the Rodeo team — brainstormed in the same room. Watching David Attenborough documentaries was helpful for finding weird animals with weird movements, says Jardel:

• For the creature's enormous right arm, their references were silverback gorillas.
• For its spidery legs, they looked at coconut crabs.
• And for the tiny legs at the back of its body, millipedes were most appropriate.

(The creature was initially slow but, as it picked up speed during the iterations, the team decided it would have about 12 legs and a tail.)

But after Pelletier pitched these visual ideas to the Duffer brothers, the team still needed to solve the “humongous” number of technical issues that lay ahead of them.

The hard part

One of the hardest parts of creating a creature out of nothing is deciding how much of it is animation-driven and how much involves simulation. The former is Jardel’s remit and the latter is Arbuckle’s. First, Jardel — whose main concern is story and choreography — animated blocks of computer-generated dough traveling down a corridor in order to give Arbuckle a starting point.

The Duffer brothers thought looking at the rotating blob was “super-boring” and asked to see some limbs in there. Jardel carried out a huge number of tests. He sent Arbuckle what the latter describes as a cage of moving volume, which he had to populate with pieces of flesh and bone that moved within the cage in a way that looked natural. Then, he covered all of this in a layer of slime and goop. It looked like “a rolling pile of garbage,” says Arbuckle.

As the motion developed and generated slime that stuck to the pieces, it began to look more like a rolling ball of spaghetti and meatballs. As Jardel says in this video, the creature is composed of 12 different skin variants, all of which look like types of salami.

Jardel and his animators carried out locomotion tests, acting out the behavior of the creature themselves in order to simulate its movement. This informed how the Duffer brothers would film the sequence. One member of the team lay with his knees on a skateboard and pushed himself around the room while approximating the facial expressions of the creature.

“It can be a really fun part of the job,” Jardel says.

“The grosser the better.”

Another challenge was just how much gore they could get away with showing. Stranger Things has prominent elements of horror, but with a young cast and audience, there’s a limit to what they can show. The Duffers want to find this line “and pretty much try and cross it,” says Pelletier. The creature needed to consist of raw anatomy, but the less identifiable that anatomy was, the likelier it was to be granted a 15 rating.

Rib cages were out. The Duffer brothers also specified that it couldn't look like a bag of babies rolling down a hallway. Arbuckle also says that when the young cast saw the first tests, “they all thought it was gross and awesome; the grosser the better.”

In order to simulate the movement of the gelatinous blob, which the team regularly compares to a slug, Arbuckle's fluid simulations approximated how particles of various sizes will behave in relation to one another while moving. Filtering techniques allowed Arbuckle to affect the smoothness of the surface. He created a “custom solver” that used particle- and position-based dynamics to build constraints between particles and let these constraints break and rip apart.

Spandex Ken

One element of the process received a lot of attention when Netflix provided a glimpse behind the curtain on Instagram.

“Just shooting at an empty hallway is not fun for anyone because, other than us on the visual effects side, no one’s able to picture what’s gonna be there,” says Pelletier.

So in order for the camera operator and actors to have something to look at, assistant stunt coordinator Ken Barefield acted as the creature while dressed in red spandex (red being easiest to animate because it most resembled the creature) and wearing a chrome ball as a hat. The creature was supposed to be under five feet tall, so Barefield spent his time crouching.

The chrome helmet was part of a standard process in VFX. A “ball pass” helps the team determine how the light in the environment looks when it is bouncing off a reflective surface and off a matte surface.

“It wasn’t the most useful thing for us,” Pelletier says of Barefield’s involvement, but having him scream and lunge at the actors must have improved their performances, right?

Working as a team

While working on the sequence, the Rodeo team generally communicated digitally, though every day in Montreal they would check their progress in a meeting hosted by Pelletier (often remotely, from the Quebec office).

“We had so much to do we could not meet too often,” says Jardel.

The frenzied nature of the work (it was between three to four months from conception to delivery) meant the team wished they could have spoken face-to-face more often. Arbuckle could have walked over to see Jardel in the office if he wanted — Rodeo has multiple buildings in Montreal and also bases in Munich and Quebec — but each department trusted that the other knew what it was doing.

Jardel believes Rodeo's work is so accomplished because, where some companies might acquiesce to whatever the client proposes, they do not.

“At Rodeo, we will really challenge a client if we think he has a bad idea,” he says, adding that the Duffer brothers were open to hearing Rodeo’s thoughts. “We really try to be a vendor that can help them artistically.”

Arbuckle believes Rodeo has struck a good balance and that the team — there were between 200 to 300 on Stranger Things Season 3 — all work well together. “The mentality of keeping around the right people that work together in the right way is important,” he says.

As the cast and crew saw Rodeo’s work, the team began to realize they had done all right.

“We felt extremely proud,” says Pelletier.

Arbuckle is less prone to self-congratulation.

“Typically, when I'm done with something, all I see is stuff I wish I could have done or forgot to do or would change,” he says. “But in this one there were several moments where I was pretty happy with what came out of the final composite.”

When the episode aired on Netflix, friends and peers reached out to say the effect had been spectacular. At the Visual Effects Society Awards, Rodeo beat shows like The Mandalorian and won two awards for their work on the show.

“That to me was pretty crazy,” says Arbuckle, allowing himself to get just a little carried away.

DREAM TEAMS is a series from Inverse that takes a look back at the greatest team efforts of the 21st century and what they mean for our ability to collaborate in the future.

Check out more Stranger Things “gross-outs” from the Rodeo FX team: