The father of the victim whose life was nearly claimed by two girls that worshipped the Slender Man has spoken out against the film, citing how they feel disgraced by Hollywood making a film about events that led to tragedy.

Joey King and Javier Botet have both played characters in the Conjuring Universe. King played as Christine in The Conjuring and Botet played as The Crooked Man in The Conjuring 2.

During the post-production of Slender Man, Sony and Screen Gems were reportedly very nervous about releasing the film due to the ongoing court cases and negative publicity surrounding the Creepypasta legend. This caused Sony and Screen Gems to release the film with very little promotional materials to it and it did not screen for critics.

Slender Man first appeared on the Something Awful forums in a series of photographs edited to depict a tall, humanoid entity unnoticed by other people in the image but almost always surrounded by, or in close proximity to, children. Since then, many have speculated inspiration and origin of Slender Man in popular media, folk tales, and ghost stories from hundreds of years ago, the earliest being a reference to Der GroƟmann in a German folk story written in 1702.

Hallie and Lizzie's last name is the same as the real last name of the original creator of Slenderman. Eric Knudsen who goes by the pen name Victor surge

Talitha Bateman was slated for Lizzie but Taylor Richardson was cast instead.

The author of the book "Bioelectric Organisms and the Paranormal" has the same name as the art director for the film.