🚨 There are MASSIVE — and I mean, MASSIVE — Stranger Things Season 4 spoilers ahead! 🚨
1. First, Stranger Things Season 4 opens with Dr. Brenner doing a crossword puzzle before going into work. One of the clues in the puzzle is "Wife of Shiva," with the answer being "Kali." This is a sneaky reference to Season 2 when Eleven found her lost sister Kali, aka Eight.
2. Dustin, Mike, and Lucas are all notably members of Eddie's Hellfire Club when they get to high school. And, in the very first episode of Season 1, Will asks for Dustin's X-Men Issue #134 from 1963 after winning their bike race, which follows the X-Men as they go up against the Hellfire Club. In the Marvel comics, this club is notably made up of evil characters, who take Jean Grey and try to use her and her powers as a weapon, which is similar to what Eleven goes through in Stranger Things.
3. Throughout Season 4, you can see that Eleven keeps her bedroom door cracked open a few inches whenever she's writing letters to Mike or when Mike's visiting from Hawkins, which is a nod to Hopper's letter to Eleven from the Season 3 finale.
4. Also throughout Season 4, you can clearly see that Eleven's still wearing the blue hair tie that Hopper gave to her in Season 2. The hair tie originally belonged to Hopper's daughter Sara before she died.
5. When Eddie is reading the Newsweek article about teenagers becoming obsessed with Dungeons and Dragons, it's similar to the news story that played during the Season 3 finale after The Battle of Starcourt.
6. When Steve is telling Robin that there's no way Vickie is straight because she returned Fast Times at Ridgemont High paused on Linda's boobs, this isn't the first time this iconic '80s movie has been referenced on the show. In the Season 3 finale, Steve reveals that Fast Times is one of his favorite movies while trying to get the job at Family Video.
7. Also, Steve remembers that Fast Times is one of his favorite films after he runs into a cardboard cutout of Phoebe Cates's Linda in her red bikini, which is the exact moment Steve says Vickie left the film paused on when she returned it to Family Video.
8. When Mike and Dustin recruit Erica to take Lucas's place for the final night of Eddie's Dungeons and Dragons campaign, and Erica is already a pro, it's a great callback to Season 3. In the Season 3 finale, Lucas and Dustin gifted Erica all of Will's old D&D supplies that he wanted to donate.
9. Also, you can see that Erica is wearing an American flag tied around her neck when she joins the Hellfire Club for their game. This is likely a nod to Erica's iconic line about not being able to spell "America without Erica" in Season 3.
10. When Tammy Thompson returns to Hawkins High from Nashville to sing the national anthem, Robin says that she does sound like a Muppet, which is a callback to when Steve and Robin were discussing Tammy after Robin came out to Steve in Season 3.
11. Also, Robin covers up saying that she had a crush on Tammy by telling Vickie about Mrs. Click's class. Robin talks about how she took Mrs. Click's class alongside Steve and Tammy in Season 3.
12. In Season 4, we learn that Vecna's victims hear and see a clock shortly before they die. If you go back and rewatch Season 2, you can hear what sounds like a clock chiming shortly after Billy is taken to the Upside Down by the Mind Flayer.
13. When we see Lucas and his basketball team crashing at Benny's old restaurant, you can see one player sleeping on a table. The image — whether intentional or not — mirrors how Hopper found Benny after his death was staged by Hawkins Lab.
14. While this ended up being a continuity error, it's still fun to point out that when Angela and her friends torture Eleven at the roller rink, you'll notice that the video recording says that it's March 22, 1986. Meanwhile, in Season 2, Joyce reveals that March 22 is Will's birthday.
15. When Dustin tells Eddie the bad news about how the police are still looking for him, he mentions using their "Cerebro," which was first mentioned in Season 3 when Dustin wanted to communicate with Suzie.
16. When Nancy decides to go and research Victor Creel, Max offers to drive Dustin and Robin, until Steve says that she's not allowed to drive again. In the Season 2 finale, Max hilariously drove Dustin, Lucas, and Steve after Billy beat up Steve at the Byers' house.
17. When Lucas gives his basketball teammates the wrong location for where Eddie is hiding, they are taken to Eleven and Hopper's old cabin that they lived in during seasons 2 and 3.
18. When Dustin is looking through the fake resume Nancy has put together, he comments on the 3.9 GPA she gave herself. In Season 1, when Steve wants Nancy to go out with him, he makes a comment about her GPA being that high so she shouldn't have to study.
19. When Robin is exploring Nancy's room for the first time, she is fascinated by Nancy's ballerina jewelry box, which is the same thing Eleven did in Season 1 when she was looking around the Wheelers' house after Mike went to school.
20. When Robin and Nancy travel to Pennhurst Mental Hospital to chat with Victor Creel, the hospital was previously mentioned way back in Season 1 when Mike, Dustin, and Lucas first find Eleven after Will's disappearance.
21. When Max is brought into Vecna's world during "Dear Billy," you can spot what appears to be a Myers gravestone, which is likely a nod to Michael Myers from Halloween. In Season 2, Max dressed up as Michael for Halloween and scared Dustin, Mike, Lucas, and Will while trick-or-treating.
22. Max escaping Vecna thanks to "Running Up That Hill" by Kate Bush isn't the first time music has been used to defeat creatures from the Upside Down. In Season 1, Will sang "Should I Stay or Should I Go" by the Clash while stuck in the Upside Down, and then, in Season 2, Jonathan played the song while Will was possessed by the Mind Flayer.
23. When Nancy, Robin, Steve, Dustin, Lucas, and Max enter Victor Creel's house and Dustin reveals he has flashlights in his backpack, you can see a Ghostbusters pin. This is a nod to when Dustin, Lucas, Mike, and Will dressed up as the Ghostbusters for Halloween in Season 2.
24. While in the Russian prison, Hopper talks about how he used to think he was cursed because of all the bad things that have happened in his life. In Season 1, Hopper notably told his girlfriend that he felt like his life was cursed.
25. After figuring out that they need a hacker to find Eleven, Will hilariously sings part of a the song from The Neverending Story, which is, of course, a great callback to when Suzie and Dustin sang it in the Season 3 finale.
26. While Eleven is training to get her powers back, she recreates the iconic Coca-Cola can crushing moment that first appeared in Season 1. In Season 3, Eleven realized she had lost her powers when she was unable to crush a can.
27. The old stuffed animal that Nancy finds in her room in the Upside Down was actually first seen in Season 1 when Jonathan sleeps in Nancy's room following their first encounter with the Demogorgon.
28. Of course, when Dustin, Lucas, and Erica communicate with Eddie, Robin, Nancy, and Steve while they are trapped in the Upside Down using the Lite-Brite, it's a nod to when Joyce used the Christmas lights to talk to Will in Season 1.
29. At one point, One shows Eleven how to escape the confines of Hawkins Lab, and he takes her to the opening of a storm drain. In Season 1, while searching the woods for Will, Hopper and Mr. Clark come across the drain and remark on how a scared child could crawl through it.
30. When Eleven watches as One takes out a bunch of guards inside Hawkins Lab and also the other children, One's fighting style matches fighting techniques we've seen Eleven use throughout the previous seasons, like having their victims start bleeding from their eyes.
31. And finally, when Eleven fights One, aka Henry Creel, you can see that she pins him up against a wall before blasting him into the Upside Down. This moment mirrors the Season 1 finale, when Eleven does the same thing to the Demogorgon.
