Nicolaus and Mona Moonbeam (Mona Månstråle), two supporting characters in the book series, are not featured in the film. Scenes featuring Mona where shot, but discarded from the final film.
Filmlance, one of Sweden's major production companies originally optioned the novel The Circle. However, due to undisclosed reasons, the authors of the book, Sara Bergmark Elfgren and Mats Strandberg, withdrew their support of the production and so did director Levan Akin. It was not until Ludvig Andersson told his father Benny Andersson about the novel and they started a production company and took over the rights that the project got moving again and the film was made.
Benny Andersson secured the rights to use Running Up That Hill by promising Kate Bush's manager to repay the favor by performing as a pianist if she needed one.
The scene in the abounded park when the blood moon appears was shot in several degrees below zero Celsius becoming particular grueling because the actresses had to be barefoot and only wearing their pajamas.
Elias has the Yu-Gi-Oh trading card "Witch of the Black Forest" in his locker.