Actor Jaeden Martell has also appeared in other films based on the works of author Stephen King; portraying a young Bill Denbrough in 'It' (2017) and 'It: Chapter Two' (2019).
Unlike It, this movie is adapted from a shorter work rather than a full-fledged novel. John Lee Hancock adapted the screenplay from the Stephen King novella of the same name. The novella "Mr. Harrigan's Phone" is included in King's collection If It Bleeds.
The Red Devil lottery tickets are a nod to the red devil killer in the Scream Queens series, which is also a Ryan Murphy production.
Although the film is set in small town Maine, Mr. Harrigan's home (interior and exterior) is, in fact, the Lockwood-Mathews Mansion Museum, located in Norwalk, Connecticut.
Throughout the film, Craig (Jaeden Martell) reads to Mr. Harrigan (Donald Sutherland). The books Craig reads are (in order as seen in the film) "Lady Chatterley's Lover"(1932) by D. H. Lawrence, "Dombey and Son"(1848) by Charles Dickens, "Heart of Darkness"(1899) by Joseph Conrad, "They Shoot Horses, Don't They?"(1935) by Horace McCoy, "The Jungle"(1906) by Upton Sinclair, "Crime and Punishment"(1866) by Fyodor Dostoevsky, and "A Tale of Two Cities"(1859) by Charles Dickens.