Raised in Hawkins National Laboratory and completely deprived of socialization, Eleven was timid, socially withdrawn and extremely cautious of other people. However, she became fiercely protective and showed unyielding loyalty towards those who cared for her, especially to Mike whom she fell in love with, to the point of sacrificing herself to destroy the Demogorgon when it threatened to harm her friends. Even after being separated for a year, Eleven showed considerable determination in saving her friends by returning to them in Hawkins from Chicago when she sensed them to be in grave danger through the Void, reuniting with them in the process. If Eleven attempted to defy Dr. Brenner's orders when under his control, she would be locked in a cramped room as punishment, potentially for hours on end. These painful experiences led her to develop severe claustrophobia. Despite her life being clouded with people manipulating and bullying her, El was shown to be incredibly empathetic, sweet, and curious about the world. Her sheltered life had left her incredibly emotional, becoming distraught easily in a dangerous or somber setting. As she grew older, El never lost her compassion, but began to be careful on who to extend that compassion to. El's friends and family were her upmost priority, willing to do anything and everything for them even if it threatened her life. Cautious and jumpy around new people though she has sympathetic and humorous moments.

Often called "Hop" Despite being the Police Chief, he didn't care about his job, regularly slept in and showed up late, and had an overall laid-back attitude in the office, even before the Byers case, and showed indifference to the cases brought to his attention. Only when Will Byers went missing, and it turned out to be a government cover-up, did he start caring about doing his job properly, as he had a personal interest in the case. After discovering Eleven and taking her into his cabin as her new home, Hopper grew to be highly sympathetic and responsible, which was why they quickly formed a father-daughter bond.

Mike is shown to be optimistic, morally compassionate, and highly committed to his friends, usually going to great lengths to help them. His D&D role as Dungeon Master suggests that he, like Will, is a creative thinker. Out of the four boys, he is the most emotionally open and open-minded, willing to accept fantastical explanations behind complex situations. After Will disappeared, he quickly drew a parallel to Will's defeat at the hands of the Demogorgon. After witnessing Eleven's psychic powers, Mike became faithful to the idea that she could help find Will. While his friends were initially skeptical about Eleven, Mike wholeheartedly trusted her to guide them and even developed a close relationship with her. Mike's slightly unorthodox approach led him to connect some of the dots explaining the mysterious Upside Down. Mike has a high level of selflessness, especially when he was unquestioningly willing to jump off a cliff to protect Dustin (before Eleven came to rescue him). Additionally, Mike displayed strong morale and courage when he confronted Troy about his joke of Will's presumed death, showing just how much he cares for his friends. Even after Will was saved, Mike perceived that Will was struggling due to his connection with the Upside Down and tried to help him. Mike was also the only one out of his friends to stay with Will in the lab when he was suffering from memory loss and was manipulated by the Mind Flayer, proving that he was always ready to put himself in harm's way to protect his friends.

Lucas kept his friend group grounded in the plausible and the pragmatic. Even during fantastical D&D campaigns, Lucas was hesitant when speculating about the more unlikely events and scenarios. He was initially wary of Eleven and her powers, which further displayed a hesitation towards the abnormal. His sustained realist approach, even during unfathomable situations, indicated that he took the task of finding Will incredibly seriously, and was determined to find him. Despite sometimes putting on a defensive and reactionary shell, Lucas was ultimately sweet-natured and had good interests at heart.

Dustin is an observer and a protector of the unity within the friend group. He frequently resolved the conflicts within the group by drawing their attention to what was going on around them. He had a neutral, level-headed approach to Eleven and the supernatural events unfolding around them; in some ways, he was a negotiator between the open-minded Mike and the skeptical Lucas. Dustin is also the most scientifically inclined of the group (despite his love of fantasy) and may be the most intelligent of the quartet- notwithstanding his bad judgement in keeping Dart as a pet, although even this unexpectedly saved the group in the end.