Forbrydelsen, a popular crime TV series that was first aired on 7th January 2007 covers the investigation of a young girl who was brutally murdered. The first season covers each day of the investigation within 20, 50-minute long episodes.
When it was originally released, it was popular in Denmark, Greenland, and the Faroe Islands, however, it soon became international - adding to its popularity. In fact, it became so popular that the US TV network AMC made an adaption of the Dutch crime show that aired seven years later, in 2014. Although this wasn't as popular as the original TV show because it seemed to "leave out all the factors that had made the original TV show so compelling".
A review of Forbrydelsen (Dutch version) on this website https://televisionheaven.co.uk/reviews/the-killing-forbrydelsen suggests that one of the reasons as to why it was so popular is because, while it focused on the investigation, it also had the main focus about how the crime itself disrupted and had such a negative impact on many lives; the family and friends of the victim, the surrounding community and even political figures. Because of this, many watchers may have found it easier to connect with the characters and became more invested in how even characters, who may seem, unimportant/irrelevant play such an important role in how people are affected by crimes committed.
One common and highly popular factor that highlights the Forbrydelsen fandom is the thick, wooly sweaters that the main protagonist, Sarah Lund, wears. These became known as the "Sarah Lund sweaters" and a huge fashion trend amongst the many people who were fans of the show - the image below shows the main actress with three women (assumably fans) who are holding a sweater that resembles her own. Jenkin's theory of Fandom can be applied here as Sarah Lund is is the narrowly defined subject of fan interest in regards to Forbrydelsen and her fans are interested in the minor details of her character such as her sweater and even her intelligence. Stranger Things is also an example as many of the viewers are interested in the minor details of characters such as Eleven and what they are interested in as explained below.
There are also some fan sites of the TV series, however, they may be more common in Denmark than they are in the West. The show, although popular does not have quite a prominent fandom to the extent that TV shows such as Stranger Things have, that may be because it is a rather mature and more psychological TV show that doesn't cover popular genres like science fiction.
Stranger Things, a highly popular TV show (first aired in July 2016) covers a series of paranormal events which take place in a Spielbergian-style town. Within the first 35 days of release, the TV series had reached a large viewership as about 14.07 million adults (18-49) had watched the show, however, this was the viewership within the US - it doesn't even cover the number of GLOBAL watchers who had begun to watch the show during the time. As suggested by the figures above, the TV series has a rather large fanbase to the extent that even minor characters, such as Barb, are extremely popular - even if they "weren't supposed to be a big deal". After the character's death early on in the series, many of her fans had sympathized with her - "#JusticeForBarb" and even created fansites/forums dedicated to supporting her. Barb's fanbases' actions had impacted how the Duffer Brothers began season two as they took inspiration from the "#JusticeForBarb" campaign and portrayed this through Nancy Wheeler and her attitudes to how the other characters reacted to Barb's disappearance/death.
The Stranger Things fandom also increased the demand for Eggo waffles because they are represented as Elven's favorite food within the show and they wanted to feel more connected with the character. Here Jenkins can be applied as the fans' interest is surrounded by the minor details of her character rather than just her powers that are highlighted throughout the series. This is one of the many examples of how the fandom grew and became more connected with the show due to cross-promotion; other examples include notebooks, clothing, cups, and even funko pop figures.
Another reason why the TV series may have such a large and prominent fandom is because of its intertextual references that bring a sense of nostalgia to the older generation who grew up watching Spielbergian movies when they were younger. It also promotes games such as Dungeons and Dragons and movies such as Never Ending Story and E.T. the Extra-Terrestrial for younger audiences and have enabled them to engage in these games and movies more than they possibly would have done before they watched the TV show. This emphasizes the fandom as the show itself refers to the interconnected social networks of individual fandoms through the heavy use of intertextual references.