From Entertainment Weekly:
“Anyone who has watched Stranger Things 2 in its entirety likely has an opinion about the seventh episode, “The Lost Sister,” which has polarized viewers since the show debuted last month. In the episode — which moves the action away from Hawkins, Indiana, and doesn’t feature the main cast save for Millie Bobby Brown — Eleven (Brown) travels to Chicago to meet her long-lost “sister” Kali (Linnea Berthelsen). Both girls were raised in Hawkins but then eventually separated. Kali is now a leader of a gang that hunts down and kills the lab employees who kept her and Eleven imprisoned.
Movie fans will likely find this dynamic familiar. The storyline was crafted by creators Ross and Matt Duffer to give Eleven the kind of hero’s journey Luke had in Star Wars, particularly Episode V. “We talked a lot about Empire Strikes Back,” says Matt Duffer. “We talked about Luke going to Dagobah and meeting Yoda. Also, the idea of a dark Eleven, of Eleven being pulled to the dark side was an interesting idea. So a lot of that episode was what happens if Eleven is drawn towards this darkness and what can she learn about herself if that’s the case.”
Without discussing the arc with the brothers, Berthelsen actually prepared for the Kali-Eleven dynamic by watching the franchise. “I took everything from Luke and from the relationship with Anakin,” says Berthelesen. “The reason why Kali is so angry is also because of love. She wants to believe in another human being. Something really went wrong and people let her down. She’s trying what she believes is the best way to support Eleven. Maybe it’s not the right way to do it but it’s coming from a good place. And I think that’s the same thing with Darth Vader — he believes it’s the right thing and he’s doing everything for the love of his mother.” […]”