Aubrey Plaza, involved in no way with the film, was such a fan of it that the filmmakers offered to allow her to host a screening. She arranged this screening at a theater in Los Angeles and invited 60 people to attend. Ten minutes before it was to begin she was informed that the film had not arrived in the theater. She went into the lobby to announce this, but mid-announcement was told the film had arrived. Everyone was seated and then forty minutes went by. She asked friends Fred Armisen and Nick Kroll, who were in the audience, to go on stage and entertain everyone. Armisen pretended to be the film's director while Kroll took questions from the audience. This lasted another twenty minutes. Ultimately the theater management said the film never arrived, but offered to show the crowd the film Suspiria (2018) instead. Then, an hour into showing Suspiria, they cut the film off abruptly and began to play Border, which had finally arrived. Plaza relayed this story on Conan (2010).
The trivia items below may give away important plot points.
The idea of trolls being "chased by lightning" and having a fear of thunder is a left over from the pagan times of Scandinavia. In the pagan belief the thunder god, Thor, would hunt giants and kill them with a strike of his hammer, i.e. a lightning strike. In later folklore this lived on as various evil creatures like trolls and werewolves being afraid of thunder.
The subplot about the pedophile ring was invented for the film and not present in the original short story. Perhaps it could be seen as a nod to John Ajvide Lindqvist's earlier novel "Let the Right One In", which included a subplot about pedophiles which was omitted from the film adaptation.