Max Mayfield and Jane Hopper

Maxine "Max" Mayfield, portrayed by Sadie Sink and voiced by Jolie Hoang-Rappaport, is a main character in Stranger Things, being introduced in the second season; she is also a main character in Stranger Things: Tales From ’85, additionally being the protagonist of the novel Stranger Things: Runaway Max. A newcomer to the Party, and the stepsister of Billy Hargrove, she is best friends with Jane "Eleven" Hopper, Mike Wheeler, Will Byers, Dustin Henderson, and Lucas Sinclair. She also has an on-and-off romantic relationship with Lucas, until they finally kept their relationship stable after enduring many horrors together. Max Mayfield loves horror movies; her favourite horror movie character is Michael Myers from Halloween. She dressed as Michael Myers to go trick or treating in Trick or Treat, Freak when she scared Will Byers, Lucas Sinclair, Mike Wheeler, and Dustin Henderson. She is also quite familiar with Ghostbusters, she also likes The Terminator as mentioned in Runaway Max.

Max was originally from California, born July 12th, 1971, and had a keen interest in skateboarding from a young age. Following her mother's divorce and remarriage to Neil Hargrove in 1984, Max and her erratic stepbrother Billy moved to Hawkins, Indiana. Max quickly gained a reputation at the Palace Arcade for topping the game leader boards, her high scores submitted under the player name "MADMAX". Max's high scores captured the attention of arcade regulars Mike, Dustin, Lucas, and Will, who mistakenly assumed her to be a boy. After Maxine joined the boys' class at Hawkins Middle School, they realised the new girl and the mysterious MADMAX were one and the same. On Halloween, Max crossed paths with the boys while trick-or-treating, and despite being weirded-out by their earlier behaviour, had a change of heart, and sought to befriend them. Dustin and Lucas, each secretly pining for her affection, wanted to make Max an official member of the Party, but Mike pushed back against the idea.

When Will started experiencing strange 'episodes', Max took notice, and became even more curious after learning of Will's disappearance the previous year. Though her new friends were initially reluctant to explain what had happened to Will, Lucas eventually divulged the whole history of events involving Will, Eleven, the Demogorgon and the Upside Down. Though sceptical at first, Max's convictions would shift after encountering a pack of faceless humanoid predators alongside Lucas, Dustin and their friend Steve Harrington. Max and her friends soon realized Will was possessed by the "Mind Flayer", a malevolent entity serving as the mind and heart of the Upside Down, whose influence in Hawkins was expanding in the form of gigantic, vine-like tunnels burrowing deep beneath the city.

Jane Hopper (born Jane Ives), also known as Eleven or El, is a main character in Stranger Things and its spin-off animated series Stranger Things: Tales From ’85. She is portrayed by Millie Bobby Brown in the original series and voiced by Brooklyn Davey Norstedt in the spin-off.

Jane was born with special psychokinetic abilities; Jane's mother, Terry, was experimented upon in the controversial government program known as "MKUltra", which, by accident or by Dr. Martin Brenner's design, affected Jane in the womb. Upon her birth, Jane was immediately kidnapped by Dr. Brenner, and brought to Hawkins National Laboratory. Jane was designated "Eleven", as one of many in Brenner's series of child test subjects. Throughout her childhood, Brenner tested Eleven and the others' abilities at the lab, all while denying her access to the outside world.

Max grew romantically attached to Lucas, but had an awkward first meeting with Eleven upon her return to Hawkins. After standing up to an erratic and violent Billy after his assault on Steve at the Byers house, Max further proved her worth, stealing Billy's car and transporting the group to the underground tunnels. There, they assisted in the fight against the Mind Flayer by attacking the Upside Down's shared hive mind. After defeating the Mind Flayer, Max attended the Snow Ball with her new group of friends, and after sharing her first kiss with Lucas, would begin a relationship with him.

In 1984, Max was originally only told of El through Mike as a girl in the Party that "moved away". When Eleven saw Mike smiling at Max skateboarding, she jealously used her powers to cause Max to fall onto the ground. When Eleven revealed that she was alive to her friends, Max was shocked that what the boys told her was true. Max approached Eleven and introduced herself, saying she had heard a lot about her and gesturing for a handshake. Eleven, however, coldly brushed her aside, much to Max's confusion. This didn't stop Max from assisting in defeating the Mind Flayer, and they later attended the Snow Ball together.

In 1985, Max and El were initially on neutral terms, both now being members of the Party. Unlike Will, Max originally defends Mike and El's relationship, calling it "romantic". However, when El approaches Max at her house about Mike ditching her, Max interprets this as Mike lying to El to hang out with Lucas. She tells El to ignore Mike's attempts to contact him and if he doesn't explain himself, to "dump his ass". To cheer her up, Max takes El to the Starcourt Mall. Though El is initially hesitant since going to a public place was against her father's rules, Max comforted her and told her that nothing would happen since she had super powers. The girls soon grew close to one another throughout the day, trying on clothes, taking photos, pranking bullies, and getting ice cream. Max encouraged El to find herself without her father or Mike's approval, and El began to copy Max, repeating many of her sayings. The girls find Mike, Lucas, and Will at the mall as well. Max defends her letting El to be in public, saying she has found her "new style". Hanging out with Max has influenced El incredibly, as she confronts Mike lying to her and eventually "dumping his ass", much to Mike and Max's shock. As the girls leave on a bus, they high-five one another while giggling. That night, Max sleeps over at El's cabin and introduces her to teen magazines, while also comforting her over her breakup with Mike. The two use El's powers to spy on the boys, and soon create a boardgame off of it. El asks if it's against the rules, but Max tells her that "[they] make [their] own rules". The game is cut short when the girls spy on Billy and discover him doing something to a screaming girl. Though Max is initially dismissive and believes Billy is just doing something sexual with a girl (as she describes to El as "happy screams"), the two eventually realize that Billy has been possessed by the Mind Flayer. Letting bygones be bygones, the girls reunite with the boys to help defeat the Mind Flayer. When Max cleans up El's neck after she has been choked by Billy, Max asks her if it hurts. El says it only hurts when she talks, causing Max to joke that she's lucky that she's not Mike because "she'd be in constant pain", causing El to laugh. When arguing with Mike, Max tells him that El is her own person, fully capable of making her own decisions, and Mike should trust her since El has saved the world twice.