D'Artagnan. Could he have been raised to view Dustin as its parent and not be like other Demogorgons if only he hadn't attacked it as soon as it became clear what it was? Do all demogorgons carry the Mind Flayer's taint from birth or was D'art possessed offscreen at some point?
Was Barb really trying to protect Nancy, or was she selfishly trying to keep Nancy from moving into a social circle where Barb would never feel comfortable?
Hopper:
In Season 2, is he keeping Eleven in secret because he's genuinely concerned over a government reprisal, or is he exploiting the situation to replace the daughter who was taken from him?
Some consider his role towards Eleven in Season 3 to be at same level of emotionally constipated roughness he's always been, or that he's reacting differently simply due to the fear of "losing" Eleven (like his first daughter) as she grows up. Others find his frequent screaming at Eleven, threatening Mike into lying to her, escalated drinking, and relentlessly negative behavior towards Joyce to be straight up Abusive Parent territory.
Did Kali project Brenner in "The Lost Sister" to have Eleven stay with her or make her chose her path to return to her friends?
Billy Hargrove:
Was Billy actually going to run over the boys? Or did he know they were going to get out of the way and he was just messing with Max? The distance he was at before revving up his engine would have given the boys enough time to get out of the way.
Billy coming on to Karen Wheeler in Season 3. Is he legitimately interested in her as a person? Just trying to score another conquest? Wanting to get back at Mike for his treatment in Season 2 by boning his mom? Or is he using an older woman to work through his mommyissues?
Will:
His Minor Insult Meltdown in response to Mike’s crack that he doesn’t like girls. Is it because he’s gay and sensitive about it (justified considering the time)? Or is it because (even if not gay) people have been hounding him about his sexuality for years and he can’t believe Mike is getting in on the act? As Season 4 heavily implies that Will has feelings for Mike, is the reason then that he's doubly hurt because he's being mocked by the person he cares for?
Will’s aversion to romance in Season 3 in general. Is he just immature? Gay? Asexual? Or does he have a Paralyzing Fear of Sexuality?
The Mind Flayer. The Reveal at the end of Season 4 shows that Vecna discovered it as a formless shadow, before morphing it into its spider form, with the heavy implication that Vecna has been controlling it all along. However, it's still unclear what exactly their connection is. Is the Mind Flayer simply The Dragon that's been Forced into Evil? Is it working alongside Vecna to take over the world? Or is it merely using Vecna as an Unwitting Pawn to further its own goals as a Multiversal Conqueror? Most of the evidence (including lines from Eleven and Will, both of whom have psychic connections to the Mind Flayer) seems to lean towards the former, but it could easily go in any of those directions.
Is Sullivan truly believing that El is the real threat and desperate to stop her by any means or is he wanting to scapegoat her as a means of either denying or covering up that the actual threat is something that is completely out of the military's control? Also, is he motivated by a genuine Well-Intentioned Extremist mindset or is he a Knight Templar who doesn't care about whether or not El is the true threat and just wants to destroy anybody with powers and unique abilities?
Or could he be a traitor serving the interests of the Soviets and manipulating the men under his command into unwittingly doing the same? Massacring fellow U.S. soldiers, intelligence agents, and civilian scientists all presumably working under the auspices of the federal government is pretty hard to square with him being an honest patriot doing his duty as he sees it.
During his speech in his first appearance, is Jason invoking the names of dead students just for the speech, or does he genuinely love Hawkins and memorialize the dead students, he just suffers from a tone problem? Yeah, it's insensitive, but he's still just a teenager trying to boost the morale of his school. He's also not just throwing their names (which he knows by heart) out for a game, he's describing a speech he made to his team when they were losing to remind them that Hawkins needed a win after all the misery of the past few years; it clearly worked, and none of his teammates act like that speech didn't happen. He starts losing his mind not long after that event so there's not much untainted evidence, but if he's the Paladin to Eddie's bard, it's only natural that his love for God and country should be so genuine it can drive him to extremism.
His crusade against Eddie is often debated as well. Was he someone who had good intentions and made logical conclusions about Eddie being involved in Chrissy's murder? Or was he someone who had a hero complex and used his girlfriend's death as an excuse to finally attack Eddie?
