Stranger Things season 2

The second season of the science fiction television series Stranger Things, marketed as Stranger Things 2, was released worldwide on the streaming service Netflix on October 27, 2017. The series was created by the Duffer Brothers, who also serve as executive producers along with Shawn Levy, Dan Cohen and Iain Paterson.

This season stars Winona Ryder, David Harbour, Finn Wolfhard, Millie Bobby Brown, Gaten Matarazzo, Caleb McLaughlin, Noah Schnapp, Sadie Sink, Natalia Dyer, Charlie Heaton, Joe Keery, Dacre Montgomery, Cara Buono, Sean Astin and Paul Reiser. Brett Gelman, Linnea Berthelsen, Matthew Modine, and Priah Ferguson also appear in recurring roles. The season received highly positive reviews, particularly for its story, character development, production values, visual effects, performances (particularly those of Harbour, Brown, Schnapp, Keery, and Astin), and darker tone compared to the previous season.

In the fall of 1984, one year after his disappearance, Will Byers and the town of "Hawkins, Indiana", once again find themselves as the target of the Upside Down. A mysterious plague begins to consume pumpkin patches around the town during Halloween season. During this, Will perceives a large and many-armed shadow entity, which the party eventually names the "Mind Flayer", that is able to possess him after an attack. Meanwhile, the larger group, including Mike Wheeler, Lucas Sinclair and Dustin Henderson encounter "Demogorgon dogs" or "Demodogs", which terrorize the citizens of Hawkins. Will's family and friends alongside Jim Hopper, Mike's sister Nancy, Nancy's boyfriend Steve Harrington, Californian newcomer Max Mayfield and a missing Eleven, must join forces to contain the threat.

With the critical and viewership success of Stranger Things after its first season's release in July 2016, speculation on a possible second season was raised. The Duffer Brothers initially intended for Stranger Things to either be a standalone miniseries or an anthology series. They also considered the possibility of setting a potential second season (which they referred to as a "sequel") in the early 1990s and featuring an older version of the characters, along with all-new characters, who are drawn back to Hawkins after supernatural events begin occurring again.

However, following the release of the first season, they realized that the likability of the characters – especially the children – was key to the series' success, and they decided to set the second season in 1984 and focus on the same characters. By the end of July, the Duffer Brothers had outlined a plan for such a season if it was green-lit, and Netflix's CEO Reed Hastings said in early August that the company "would be dumb not to" renew Stranger Things for a second season. On August 31, 2016, Netflix announced it had renewed Stranger Things for a second season of nine episodes, to be released in 2017. The Duffer Brothers revealed that the series had been renewed for a second season before the first was released. Regarding the decision to wait more than a month after the first season was released to announce the renewal, Matt Duffer said, "it actually ended up working because it had built up to this fever pitch. I guess that's what [Netflix] were intending to do all the time."

The success of the first season led the Duffers to let their writers' room propose any idea they could come up with out of desperation for ways to expand the show. However, Ross Duffer stated in the WGFestival 2022 that thanks to the writers proposing more ideas than necessary, they were forced to drop some. Several of the unused ideas for the season were later included in the fifth and final season. The Duffer Brothers wrote the second season to make the combined first and second season feel like a complete work, but set elements in place to go forward with additional seasons if they were green-lit. While most of the story for the second season had been decided before the first season aired, the Duffer Brothers took in the audience reactions from the first season to adjust some of the details within the second season. They knew they would not have the same element of audience surprise as when the series aired anew and were aware fans wanted to see certain elements, but Ross said "...the point is not to give everyone what they think they want. Because I don't think they really know what they want."

The Duffer Brothers felt that the second season should be treated more like a sequel rather than a continuation, and thus opted to call the second Stranger Things 2. This approach had some trepidation from Netflix, since the company felt movie sequels typically have a bad reputation, but the Duffer Brothers pointed out that there had been many successful sequels that surpassed the original film, and felt confident with this name. Despite revealing episode titles for the season in the announcement teaser in order "to provide some hint of where we were going in season two without giving anything away," Matt Duffer stated that some of the titles would change since there were some things "we didn't want to put on there because we felt like it would give too much away," and because "people are smart on the fucking internet" with fan-created "videos analyzing the chapter titles... right on a lot" of how the titles related to the plot of the season. In early October 2017, the Duffer Brothers revealed the final titles for the first six episodes of the season.

In October 2016, it was announced that Schnapp and Keery had been promoted to the main cast for the second season, after each recurring in the first season, and that Sadie Sink and Dacre Montgomery would join the main cast as Max and Billy, respectively. In order to get the role, Sink told to the crew while auditioning that she knew about rollerblading and skateboarding; Sink actually knew how to do the latter but not the former, reflecting years later during an appearance in Jimmy Kimmel Live why did she think lying would help her nail the part as the two things weren't quite the same as she thought. Ryder, Harbour, Wolfhard, Brown, Matarazzo, McLaughlin, Dyer and Heaton also return for the season. Sean Astin as Bob Newby and Paul Reiser as Sam Owens are also part of the main cast in the season. For Owens, The Duffer Brothers had referred to the character in their pitch to Netflix for the season as "Paul Reiser", and specifically alluded to Reiser's character Carter J. Burke in Aliens, with Ross referencing James Cameron's casting choice for that film, saying, "[Cameron] thought people would inherently trust [Reiser] and it would be a twist". Reiser's son was a fan of Stranger Things, and gave his father an early appreciation of the series so that when the production called his agent about the role, Reiser was excited for the part. Joining them in recurring roles are Linnea Berthelsen as Kali / Eight and Brett Gelman as Murray Bauman.