Peter Jackson’s New Zealand-based company Wētā FX is used to working on ambitious projects. But even by its standards, the fifth season of Stranger Things proved to be a beast. Wētā’s Emmy-nominated visual effects team had to seamlessly blend organic action and digital effects to immerse fans in the world of Hawkins, Ind., as well as its menacing flip-side, the Upside Down.
Luckily VFX supervisor Martin Hill and his team — which also included animation supervisor David Clayton and VFX producer Richard Thwaite (who has since left the company) — were fans of the series, and excitedly joined Season 5 near the end of 2023. Hill first met with creators Matt and Ross Duffer, as well as the show’s visual effects supervisor Betsy Paterson and VFX art director Michael Maher Jr. The epic job was finished in October 2025, a few weeks before the show returned in late November on Netflix.
VFX work on the episodes was both sequential and concurrent, and the team had many sequences to jump into right away. The Duffers wanted the monstrous Demogorgons to be larger in the frame, as well as upscaled, more detailed, and more nuanced. There was also an enhanced role for the Demodogs, as well as Vecna 2.0 — a scarred and more organically fluid iteration of Jamie Campbell Bower’s villain, as well as the epic battle between our Hawkins heroes and the giant, 120-feet-tall Mind Flayer.
The Mind Flayer ultimately had 22 legs, but at one point the VFX team contemplated 28, with six additional legs that could shoot out of its mouth which would have been more frightening. But Hill observed that they didn’t want to “overcook the design.”
For example, when the giant monster has Nancy trapped in a tight canyon crevice and is trying to get to her, greater jeopardy could have been created with the revelation of additional legs. But in a sequence with fast cuts and many protagonists involved in the melee, “suddenly introducing a new VFX element would have been possibly distracting,” Hill muses.
It also would have changed the stakes and execution of a large sequence that had already been worked out extensively in the pre-vis stage. “We told the story more by the Mind Flayer’s face just getting really, really close. There’s a bit of an homage to Alien 3 in there, where the Mind Flayer’s face gets really close to Nancy.”
The Mind Flayer finale had 453 effects shots, while the whole season totaled 1,190. Hill says that “1,800 would be all of a very large VFX heavy feature. That would be a Return of the King level amount of shots.”
A pre-vis version of the Mind Flayer
Creating the charred Vecna was crucial for his dramatic re-emergence during Season 5’s fourth episode, with Hill noting that they they wanted him to be “the embodiment of evil” during his “Darth Vader moment.” Because Bower is quite slender, Hill says they decided to bulk up his character with “all the corruption and the vines and tendrils from the Upside Down.” Bower was open to having extra padding in his costume.
“Although we’re only using a tiny bit of his eyes, and often not even that, he’s basically fully digital in this stage,” Hill reveals of the new Vecna. “Whereas in Season 4 he was basically all practical with a bit of digital on top. We were still using his performance … and we used the cadence and his timing and his footsteps to be this bigger, more frightening guy.”
An addition to Vecna’s physiology were the tendrils that shoot out of his left arm, an idea conceived by the Duffer brothers. “Early on in development, one of our effects supervisors, Yas Arahori, did this design of these stretching tendrils and different ways he could attack the soldiers that are in the DMZ,” Hill explains. “He had tendrils wrapping around their neck and strangling and maybe rolling around their face and gouging their eyes.
“In the end, we did one we just thought was so over the top where the tendrils punctuate through the back of this guy’s skull and through his eye sockets,” he adds. “That made it into the final cut. That’s the end piece, the last soldier on the ground.”
Bower on the ‘Stranger Things’ set as Vecna
Other evolved baddies for season five were the Demodogs. As Hill describes, the Demogorgons were a bipedal humanoid form that could also run on four legs. They wanted to make the Demodogs distinct, so they motion captured a group of dogs to give their onscreen alter egos skitterish mobility.
“When they’re running around corners they slide a little bit,” Hill says. “We were motion capturing them on a slightly slidey floor, and they were all scrambling with their legs. It almost got a bit too cute. We have all this motion capture of these dogs having the time of their lives on the motion-capture stage, and they’re wagging their tails. There are certain takes where the Demodogs were chasing everyone through the hospital, and they were wagging their tails. It was just a little bit too cute, so we toned that down. But there is an element of that dog personality that comes through.”
The dogs’ final shot, just before they get blown up in a hospital dryer, was memorable. “The dogs are looking in, and one of them just cocks his head as he realizes what’s going on,” Hill says. “It’s a very dog-like motion, and just for a moment we feel a little sorry for them.”
For Season 5, the Duffer brothers wanted more intense Demogorgons so motion capture was often used to get more nuanced performances. “We had a lot of these creeping, stalking shots, and the Duffers really wanted to see them thinking,” Hill explains. “It needed to be this sinister, predatory creeping, showing the intent. They’ve got no face. We’re really putting the performance into the shoulders and the hips and the creeping motion and then just little hints with the petals. They have the five petals around [them] that are almost acting like eyebrows in a performance sense.”
A pre-vis Demogorgon
In the scene where Holly’s mom Karen (Cara Buono) vehemently defends her daughter from a Demogorgon by wielding a broken wine bottle, the team had to make it believable that a creature that cannot be killed by ordinary gunfire can be subdued by an incensed woman with a piece of sharp glass.
“A stunt guy was standing in for the Demogorgon with a pad there, and Cara was really hitting that pad and raining blows against it,” Hill recalls. “It was a really impressive performance, and she was just furious.”
He notes that there was a shot of the Demogorgon where it pulls back “and it’s almost got a grill of all these bits of green wine bottle lodged in between its teeth which is a great touch of little blood splaying everywhere. We wanted to give it a little bit of a surprised look because it sees Karen, it sees Holly. He’s found them. He just needs to drag them off, and then he’s totally taken back by the ferocity of the attack.”
A pre-vis Venca
Another gnarly look for the season was Vecna 2.0 who has been burnt and charred with a painful look reflective of his experience.
“One of the first things that we did when we started designing him was, in a very antipodean way, have a barbecue,” Hill reveals. “We took lots of meat and stuff from the butcher, and we wrapped it in latex and all these other things for skin layers, and cut gouges and things in it. We cooked it, burnt it, and took crème brûlée torches to it.
“All that didn’t just serve as reference,” he continues. “We scanned all that and it’s used as part of the creature. It’s the same for the inside of the Mind Flayer — taking that same visual language and transferring it over because there needs to be a connection between the two. All of the membranes that are inside the Mind Flayer are a combination of things that come from the Rift and things that come from Vecna. We designed that digitally and then we exported it, and we printed it out on stage.”
The Wētā team built a half-height stage that matched the CG and which the actors could act on for more performance authenticity. They rescanned the stage back in digitally because of changes made when it was being built. “Then we had perfect correlation between the digital environment and the set environment, so they could really perform in the stage which is super important,” Hill says.
Another big challenge was capturing Vecna’s emotions from Bowers’ nuanced portrayal which included his facial performance and his dialogue. They wanted Vecna to look believable, especially in all the back and forth with Will (Noah Schnapp). Unlike the perpetual mo-cap approach of James Cameron’s Avatar movies, the Duffer brothers were shooting on physical sets and on real locations. “The actors being able to get right up in each other’s faces without cameras in the way and perform off each other,” Hill says.
Instead of animating Vecna’s face to match Bowers performance, Hill’s team wrote an in-house tool called Thistle “which used optical flow to attach the performance onto Jamie’s face,” he elaborates. “It really was Jamie’s performance, even though everything was digital, and it needed to be digital because we had these flowing tendrils all over its face and body.”
The actor playing young Will Byers
An unusual and unexpected challenge was bringing back the younger Will from Season 1 for Season 5. Because no one anticipated the show lasting this long — and given that Schnapp’s character disappeared throughout most of the first season — no scans of him were available and minimal photos existed. The Wētā team scoured through the proverbial cutting floor, from official footage to outtakes, for reference.
“Then we started replicating shots from Season 1 that he was in digitally to be able to validate our model,” Hill elaborates. “Does it look like Will? Can we replicate this shot? Until the point where the Duffers and Betsy and Michael were really happy with it, and then we had to essentially put him in the Upside Down for however long it was. We needed to make him look really pale and really tired and really ill, and his iconic bowl cut was now this bedraggled mess.”
The final version of young Will Byers
Taking in all of Wētā FX’s accomplishments on Stranger Things’s fifth season, one must imagine that it was a relief to finally get it all done. But it truly was a passion project for Hill and his crew.
“It was an awful lot of work, and we had the best team doing it,” Hill declares proudly. “It was a lot of fun. We were all really sad when it was over.”
Swipe through a gallery of behind the scenes images revealing Weta FX‘s work on key Stranger Things Season 5 sequences