The scene in which Margaret Matheson exposes a psychic healer by listening in on a partner feeding him instructions wirelessly was based on the case in which skeptics James Randi and Steve Shaw (better known under his stage name Banachek), with technical assistance from crime scene analyst and electronics expert Alexander Jason, exposed Peter Popoff in 1986. In that case, as in the scene, Popoff's wife Elizabeth was feeding him information that she and her aides had taken from prayer request cards filled out by audience members over wireless radio. Some of the dialogue is taken almost verbatim from the actual case. In May 1986, Randi presented the evidence on The Tonight Show Starring Johnny Carson (1962), exposing Popoff's fraudulent practices. In 1987, Popoff declared bankruptcy, only to make a comeback in the late 1990s and early 2000s.
The black and white clip of the Russian woman moving metal objects and matchsticks around on a table shown by Tom Buckley (Murphy) in class, is the same clip used in The Atticus Insitute (2015), another film about clairvoyants.
Toby Jones, Elizabeth Olsen, and Sigourney Weaver appeared in the Marvel Cinematic Universe. Jones as Dr. Arnim Zola in Captain America: The First Avenger (2011) and Captain America: The Winter Soldier (2014), with Olsen appearing as Wanda Maximoff (Scarlet Witch) in Captain America: The Winter Soldier (Post Credit Scene), Avengers: Age of Ultron (2015), and Captain America: Civil War (2016), and Weaver having a role in The Defenders (2017). On DCs side, Cillian Murphy appeared in all three Dark Knight movies as Dr. Jonathan Crane/Scarecrow, and Burn Gorman portrayed Stryver in The Dark Knight Rises.