See Stranger Things’ Millie Bobby Brown & David Harbour Reunite

1. After working on M. Night Shyamalan's Fox series Wayward Pines, brother writing duo Matt Duffer and Ross Duffer came up with the concept for Stranger Things, though it was initially called Montauk. 

"It's very hard when your brain is latched onto a title, it's really, really hard to get people to agree and accept another title," Matt told The Daily Beast in 2016. "Initially when we came up with this title Stranger Things, it was hard for people to embrace."

2. The Duffers envisioned filming the series on Long Island, but it ultimately proved to be too challenging. 

"We liked Montauk, because we liked the coastal setting, and Montauk was the basis for Amity, and Jaws is probably our favorite movie, so I thought that that would be really cool," Matt explained to The Hollywood Reporter. "Then it was really going to be impossible to shoot in or around Long Island in the wintertime. It was just going to be miserable and expensive."

Atlanta ultimately became the home base for production.

4. To play Eleven, then 12-year-old Millie Bobby Brown had to say goodbye to her hair.

"The day I shaved my head was the most empowering moment of my whole life," the actress reflected during PaleyFest in 2018. "The last strand of hair cut off was the moment my whole face was on show and I couldn't hide behind my hair like I used to. As I looked in the mirror I realized I had one job to do: inspire...You don't need hair to be beautiful."

5. She drew inspiration from Charlize Theron in Mad Max: Fury Road, as well as costar Winona Ryder's old yearbook photos.

"Winona looked cool back in the day with the pixie cut," she shared, "and I thought maybe I could bring it back!"

8. When it came to finding their Mike, the brothers had a different idea for the character. That is, until Finn Wolfhard auditioned. 

"Originally Mike was a sigher, he was a dreamer, he was much more like Mikey in The Goonies in a lot of ways," Matt told The Daily Beast in 2016. "But Finn had this really anxious, twitchy energy about him and we thought that that was really great and we just kind of wrote the character to match him and his personality."

11. In early 2018, David Harbour went viral after he fulfilled a fan's request to take her senior portraits with her after. She tweeted, "How many retweets for you take my senior photos with me," to which he replied, "25k. And I get to wear the school sweatshirt and hold a trombone." The actor held true to his word.

As he wrote on Instagram at the time. "Voted most likely to hijack someone's high school senior photos 24 years later."

15. And when the pair had to smooch again the following season, she revealed what her costar whispered in her ear.

"He wanted to let me know he was, like, kissing me then," she explained during a 2017 appearance on The Tonight Show. "So he was like, 'I'm coming in,' and he was like a ventriloquist! It was the craziest thing."

16. Natalia Dyer and Charlie Heaton, who play love interests Nancy and Jonathan, began dating in 2016, but have mostly kept their relationship private.

"That's something important to me—with my family, with my friends, I really like to keep it for me," Natalia told Refinery 29, though she did admit, "It's an interesting thing to work with somebody who you go home with. It's always really fun."

17. Believe it or not, Joe Keery's well-coiffed Steve Harrington was not supposed to make it out of season one alive.

But, "we fell in love with him during the making of season one, which is why we ended up writing that arc for him where he's helping to save the day with Jonathan and Nancy," Ross told The Hollywood Reporter. "Steve was supposed to be this jocky douchebag, and Joe was so much more than that."

18. Also slated to perish was Eleven. Yes, really. 

"Eleven was going to sacrifice herself to save the day," Ross said in the 2018 book Stranger Things: Worlds Turned Upside Down. "That was always the end game. But once we realized that the show was potentially going to go on longer than one season, we needed to leave it more up in the air, because deep down we knew the show just wouldn't really work without Eleven. And at that point, we knew how special Millie was. If there was going to be more Stranger Things, Eleven had to come back."

19. The seventh episode of season two—titled "The Lost Sister"—almost never made it to air, with the Duffer brothers telling Vulture they were concerned the outing, which centers on Eleven going off to find another child who was experimented on, would break up the story's pacing.

"When we got to the point of writing the episode, we wanted to see if we really needed it or not," Matt explained. "We actually did toy with pulling the episode completely, but then the ending with Eleven didn't work at all. It just didn't land at all. Then we ended up deciding we needed it."

20. Eleven's sibling was written to be a boy, with the episode originally titled "The Lost Brother." 

21. Bridgerton actress Nicola Coughlan initially auditioned for the role of Robin before booking the role of Penelope Featherington years later. Maya Hawke ultimately nabbed the part, with Nicola saying Hawke was "was far better than I ever would have been."

She added, "It's a good lesson to actors: Watch the stuff you didn't get, because you'll totally understand how it's not personal. You're just right for some things and you're not right for other things."

23. To win the part of Billy, the mullet-rocking bad boy older stepbrother of Max (Sadie Sink), Australian actor Dacre Montgomery filmed a fun, yet slightly raunchy, audition tape, telling GQ he "wanted to make a bit of a splash with the Duffers."

That meant filming himself dancing to classic 1980s songs like "Come on Eileen" and "Hungry Like the Wolf" in nothing but a G-string. Dacre admitted he had some hesitation about sending it, saying, "Either I'm never going to work again, or somebody somewhere is going to see one thing in me, and they'll give me a chance." Fortunately, his risk paid off.

26. Given that the younger cast was still growing as the series was filming, the wardrobe department faced a unique challenge when it came to continuity. 

"It's crazy," costume designer Kim Wilcox told E! News. "We had one kid we could not keep in shoes, like every three weeks he grew a half-size." Her solution was to find heritage brands that make the same product in multiple sizes. "We'd buy five of them so that when somebody grew we'd have something."

27. While the Duffers were paying homage The Goonies, E.T., and Stand By Me, they were cautious not to be too overt in their references.

"When we billed the project to Netflix, we had this big two-and-a-half-minute trailer that had about 20 or 30 of these movies kind of woven together to try and tell the story of Stranger Things, but obviously all these images or ideas were in our heads," Matt told The Daily Beast. "Those are the movies that we grew up on and they're so much a part of our DNA. But then when you get into the writers' room and you're working on individual episodes, actually very little time is spent referencing other movies. Mostly you're just trying to tell the story, letting the characters guide where everything's going. Otherwise it would just be a jumble and a mess."

28. The creative team set out to use as little special effects as possible to achieve a throwback feel, but quickly learned how difficult that would be.

"The funny thing is that the original goal was to do entirely practical effects. But what we realized—and it really made us admire those guys who did The Thing and Alien and whatever—is that doing practical is really hard," Ross explained. "It takes a lot of time and preparation. We were turning out scripts as quickly as we could but they don't have six months to prep this stuff. You show up on set and stuff that seemed like it would be a great idea to do in that old school way, we didn't have time to do."

30. While an ending for Stranger Things has been set, the Duffer brothers aren't ready to leave the Upside Down just yet.