Instead of suffering from the sophomore slump that plagues so many television shows, Stranger Things season 2 hit the ground running and capitalized on some of the best and most beloved aspects of season 1. The show may have started as an homage to the 1980s, but in season 2, it continued to expand and grow alongside its characters. If fans disagree about which season of the show was better, then that's only a testament to overall strength of the show.
Season 1 of Stranger Things acted as a mystery, as the audience learned the supernatural answers to questions alongside the Hawkins Middle School AV Club. In season 2, the kids of Hawkins ended up pursuing a number of different side plots and adventures, which served to further develop them as characters. In season 3, if the Duffer Brothers want to expand and capitalize on the best parts of the previous seasons, they should make sure that the gang stays together in season 3. Some of the biggest highlights from the previous seasons have been when a gaggle of Hawkins kids are together: the D&D campaign, the bicycle chases, "She's our friend and she's crazy!" Likewise, one of the highlights of season 1 is when the teenage trio - Nancy, Jonathan, and Steve - join together to fight the demogorgon.
In season 2 there is a greater fracturing, and the larger group sequences become rarer. Mike, heartbroken and traumatized, is upset that everything seems to be "going back to normal" and that the world is going on in Eleven's absence. Lucas and Dustin begin to have a hormone-fueled rivalry that begins as congenial, but seems to pull them apart. Dustin's choice to keep Dart secretly further pushes his story line away from his friends. Additionally, Nancy begins the season with Steve, only briefly interacting with Jonathan; however, she soon breaks up with Steve and joins forces with Jonathan to expose the Hawkins National Laboratory.
By the end of season 2, the story lines and characters begin to converge, but even in the amassed group of the final episode, many of the interactions revolve around two individuals who have broken away from the larger unit.
There are opportunities abound for including characters who have had more solitary plot lines within the group dynamic. Will (Noah Schnapp) is by himself in the Upside-Down for most of season 1. While season 2 showed off Schnapp's impressive talents as an actor, Will was possessed for much of the season, limiting his interactions with the other members of the AV Club. Similarly, Eleven had limited interactions with the Hawkins AV Club for the majority of season 2.
In a similar vein, season 2 saw the introduction of "Mad" Max, but Max's inclusion came at a fracturing within the AV Club - in fact, some of the boys see Max's presence as a threat to their friend group. At times, because of this, Max feels more like a plot device than a character in her own right - an object of the boys' desire or frustration that spurs on their confrontations. Additionally, Max spends much of the second season in the dark about what is going on, and because of this ignorant position, she doesn't contribute to the plot development. Because of both of these dynamics, Max is never truly integrated into the AV Club in season 2, and the audience doesn't see how she functions within the group, even as she develops individual relationships with Lucas, Dustin, and Mike.
One of the highlights of season 2 was the relationship that developed between Dustin and Steve. This unlikely duo was brought together when Dustin couldn't reach any of his Hawkins AV Club and needed help. As a result, the audience got to watch two characters that they love interact and see an unlikely friendship bloom. After two seasons, the audience has a firm grasp on the show's concept and characters, and so there is ample opportunity in season 3 for new interactions and group dynamics.
The first season generally distanced the AV Club from their high school counterparts, but season 3 could bring the two separate groups closer together. Given that in the next year the Hawkins AV Club will begin high school, Nancy and Jonathan will be at school alongside Will, Mike, Lucas, Dustin, Max, and Eleven. That's right: season 3 is going to take on high school like never before. Additionally, while Steve will have (presumably) graduated, if he is still in town, his relationship with Dustin could mean that he interacts with members of the Hawkins AV Club (and by extension, with Nancy and Jonathan). The upcoming season could explore how Nancy and Jonathan's relationship affects Will and Mike's friendship, or how Dustin's interactions with Steve and Nancy put him at odds with one or the other, or how Eleven adjusts to school for the first time - if that doesn't scream Carrie, then what does?
Additionally, season 3 should expand on the characters who have been previously isolated or have changed dramatically over the past season. How does Eleven's return affect the group, especially now that she will be joining them at school? What do Eleven and Max's interactions look like, and if Eleven's jealousy has subsided, what does their friendship look like? And, once again, how will Will reintegrate into the Hawkins AV group after yet another traumatic year thanks to the Upside Down? These characters have proven that they can be interesting and engaging, but in comparison to Dustin, Lucas, and Mike, they haven't had as much time to fully develop within the group.
Season 3 is an exciting opportunity for the Duffer Brothers to take their beloved characters on new adventures through the dangers of the Upside Down and, perhaps more terrifyingly, high school. To grow from the best parts of the last two seasons, season 3 should be built around gathering these characters together and exploring the group dynamics that play out with different combinations of characters.