Stranger Things fans have been left furious after spotting what they claim is a damning clue about the finale of season five in a blink-and-you’ll-miss-it moment.

Netflix released a behind-the-scenes look at the making of the final fifth season of the sci-fi show, which gives insight into writers and directors the Duffer brothers’ making-of journey from the finale’s start to end.

One Last Adventure: The Making Of Stranger Things 5 allows fans to meet the teams bringing together the season, which was filmed in 2024, as well as go behind the scenes with the actors on set, to make-up and wardrobe, and the table script reads.

Cameras were given round-the-clock access to the making of the season, including sitting in on script-writing sessions between Matt and Ross Duffer.

Aside from chronicling the 237 days of filming, and the 630 hours of footage filmed, the documentary gave insight that the Duffer brother’s were yet to finish writing the script before the show went into production.

In the opening minutes of the documentary, they reveal: ‘We went into production without having a finished script for the series…’ admitting they were unsure of main character Eleven’s ending until the very last moment.

Filmed as they were speaking around a writer’s table, Matt and Ross are seen debating the ending for the iconic character, played by Millie Bobby Brown.

Later, the duo sit down once again to discuss the scripts, with Matt saying: ‘This show is so large and there’s so many pages to shoot, Ross and I can simply not direct everything, it’s impossible.

‘We were either going to have to rush the scripts and not have the quality we wanted in order to direct them all… from that point on we had directors on board every season.’

In a blink-and-you’ll-miss-it flash, eagle-eyed fans were quick to point out that in both sit-down scenes with Ross and Matt, flashes of their laptop screens are shown on camera.

Viewers alleged they had spotted the logo for AI platform ChatGPT, sharing screenshots of the laptops and pointing out tabs on the laptop screen that they claimed showed the AI platform’s icon, a round geometric design.

Others alleged that on another screen, the writer’s appeared to be looking at Reddit, which is well-known for fans to discuss the show, including their theories for the direction of the series, in chatroom forums.

Taking to X, formerly known as X, cinematography magazine A Shot penned: ‘The Duffer Brothers had three ChatGPT tabs and one Reddit tab open while writing the ending of STRANGER THINGS.’

Others were quick to jump on the bandwagon, with one writing on Reddit: ‘The Duffers were seen opening 3 ChatGPT tabs while writing their script in the documentary!’

Another social media user penned: ‘Duffer brothers trying to convince us they’re some kind of geniuses that planned this whole story in 2014, whole time they used ChatGPT, Reddit and looked up “Stranger Things 5 theories” on TikTok.’

‘I wasted 2 hours of my life just to see that the Duffer brothers used ChatGPT, had Reddit tabs opened, ignored other writers pointing out inconsistencies, scrapped “ideas” they had, and started to film before they even had the finale written,’ another fumed.

Someone else wrote: ‘I knew it There were multiple times throughout Season 5 where I said out loud: “that dialogue sounds just like GPT”.’

‘The Great Duffer brother used ChatGPT to write Stranger Things Season 5. WTF man, now we know why it sucked,’ another penned.

While other fans hit out: ‘You literally see them in the documentary using ChatGPT. They also admit to filming before they even had an ending for the season.’

Others stepped in to defend the brothers, with one writing: ‘This is not conclusive evidence that they used ChatGPT to write. But it’s definitely not a good look.’

‘This doesn’t prove they were using it to write their script. Correlation does not equal causation,’ someone else chimed in.

‘I see a lot of indecipherable tabs,’ a third wrote. ‘You can use ChatGPT to give you feedback on writing (grammar, structure, word repetition) without using it to write the script itself.’

‘I didn’t like the ending either but if you look at a higher resolution screenshot it’s not ChatGPT. Just because one person says something doesn’t make it true,’ a fourth penned, sharing a high-resolution image of the laptop screen.

The image showcases that the icon thought to be for ChatGPT as a blue circular icon from a different website that some fans suggested was screenwriting software, WriterDuet.

The software is used to allow multiple writers to work on the same script simultaneously, featuring the industry-standard formatting for screenplays, novels and stage plays.

The Daily Mail have contacted Netflix for comment.

Furious fans have been up in arms since the release of Stranger Things’ finale on New Year’s Day – as the sci-fi series came to an end after ten years.

Viewers tuned in to watch the final episode of the sci-fi hit show on New Year’s Day, which drew to a close the winding story of Millie Bobby Brown’s Eleven and her band of friends in the fictional Indiana town of Hawkins.

The action-packed two-hour episode saw the group of teens, made up of Will, Mike, Dustin, Lucas and Max, and their siblings and pals, Steve, Nancy, Jonathan and Robin, take on bad guy Vecna in one final battle.

With the help of beloved characters Joyce, Hopper and Murray, season two star Kali, the friends launched an interdimensional attack against Vecna, known also as 001, Mr Whatsit and Henry Creel, and his master, the Mind Flayer.

Winona Ryder’s Joyce was seen taking the final strike at Vecna, chopping off his head, after the Mind Flayer – a spider-like creature – was brought down.

And with that, it spelled the death of Henry Creel, who as a young boy was revealed to have been taken over by other worldly dark matter.

It also meant that young break out character Holly, and her school-aged friends, could be saved from the grips of the Mind Flayer after being kidnapped by Henry Creel, disguised as Mr Whatsit, earlier in the series.

In a heartbreaking twist, their eventual victory came at a cost as Eleven, who has been portrayed by Millie, 21, since the series launch in 2016, appeared to die.

Sacrificing herself as the gate to the terrifying Upside Down, the gateway between the real world and the Mind Flayer’s desert-like abode, Eleven disappeared as the other worldly dimension was destroyed.

In a sunny flash forward 18 months later, the town of Hawkins had been rebuilt and friends Mike (Finn Wolfhard), Will (Noah Schnapp), Lucas (Caleb McLaughlin), Dustin (Gaten Matarazzo) and Max (Sadie Sink) were back to ‘normal’ life.

The episode was ended with an emotional scene seeing the pals play one final game of Dungeons and Dragons, a board game that has long been intertwined with the story since it first hit screens on Netflix.

During the final scene, Mike revealed his belief that Eleven, also known as Jane, is still alive and out there in the place they’d always said they would run away to: a remote area with three waterfalls.

He tells the group a story explaining he believes Kali, Eleven’s long-lost ‘sister’, had used her own powers of illusion to make it appear Eleven had died in the destruction of the Upside Down.

With high levels of anticipation from fans for the finale, which comes almost ten years after the first episode dropped in 2016, the ending was divisive among viewers.

While some praised the ‘nostalgic’ ending, others felt there were many unanswered questions in the finale for it to truly spell the culmination of the series – with some hitting out against the writers, the Duffer Brothers, for ‘a series of plot holes’.

It saw a growing fan theory begin circulating online, called Conformity Gate, which suggested the ending viewers saw was not the real one.

Some fans believed that another episode is due to drop on January 7 after a series of clues pointing towards the date, suggesting the finale was just an illusion created by show villain Vecna – who is still alive.

Fans took to social media to compile evidence for the case, pointing towards a series of inconsistencies in the story which would suggest the seemingly perfect ending has been manufactured.

The most talked-about example came from the graduation scene at Hawkins High, which sees Will, Max, Dustin, Lucas and Mike waving goodbye to their high school.

In the scene, the graduates are sitting with their hands crossed against their laps, holding one in front of the other – a signature pose held by Henry Creel, and those possessed by him, throughout the show.

While the graduates themselves are wearing orange gowns, instead of the green gowns fans had expected after finding a clue in a book from Nancy (Natalia Dyer).

While members of the Wheeler family, including Nancy, Mike and mum Karen (Cara Buono) also debut hairstyles that are eerily similar to Henry’s.

Fans pointed out that both Mike and Nancy have ended up being exactly what they feared throughout the series: just like their parents – living a small town existence, with Nancy dropping out of university to write for the local paper.

Speculation was further fuelled as fans spotted a blank yellow poster being held up in the background of the graduation – with yellow noted earlier in the series as missing from one key scene as Holly (Nell Fisher) and Max delve into Henry’s memories.

Elsewhere, at the WSQK the Squawk radio station,  the dials shift in colours between episodes from grey to red – and Robin (Maya Hawke) in her final broadcast tells listeners that Hawkins isn’t ‘what she remembers’ anymore.

Viewers also pointed out a number of actors are also breaking the fourth wall in the final scenes, including staring down the camera lens at the graduation, and during the dinner that see Hopper (David Harbour) and Joyce get engaged.

Background details picked up by fans also show a number of board game boxes littered in different scenes saying ‘WHATZIT’ – which some fans believe is a reference to Henry’s disguise as Mr Whatsit.

While in the final D&D game, as the characters put away their game books, their initials in one shot subtly spells out ‘X A LIE’, which fans have interpreted as a message to show Dimension X, the home of the Mind Flayer, was an illusion.

Others noted that new character Vickie (Amybeth McNulty) and Dustin’s spring fling Suzie (Gabriella Pizzolo) were both missing from the finale.

These were the two characters Vecna did not know about, and therefore could not include in his allegedly fabricated ending, according to fans.

In the final shot of the series, a Stranger Thing’s players manual is seen beside a 20-sided die, which viewers pointed out shows the number 7, linking it to January 7.

Recently The Duffers told Netflix’s Tudum that they felt they had compiled an ending that would satisfy viewers, tying up loose ends for the main characters.

Matt said: ‘More than I would say is typical, we really talked a lot with all the actors to make sure they were content with where their characters ended up. That was important to us.’

Stranger Things is available to stream on Netflix now