On William Friedkin's passing, writer and film critic Ed Whitfield posted this on Twitter(X) and Facebook :
"William Friedkin once said to me, 'Ed, the guy who made those new Halloween sequels is about to make one to my movie, L'Exorciste (1973). That's right, my signature film is about to be extended by the man who made Délire Express (2008). I don't want to be around when that happens. But if there's a spirit world, and I can come back, I plan to possess David Gordon Green and make his life a living hell.'" Friedkin actually died two months before the movie was released.
Ellen Burstyn had turned down reprising her role and was then offered double the salary. Burstyn thought, "I feel like the devil is asking my price." She eventually accepted, using the salary to fund an MFA scholarship for actors at Pace University where the Actors Studio teaches the program. Burstyn is a lifelong member of the Actors Studio and a co-president.
Linda Blair, Regan in the original 1973 film, was an advisor on set to the actresses portraying the possessed girls in this film.
William Friedkin, director of the original L'Exorciste (1973), famously hated the prospect of this sequel, but he was also dismissive of most of the previous successors to his movie. In an interview with IndieWire, he stated that he has never seen any of them including the series L'Exorciste (2016), and not even L'Exorciste, la suite (1990), which was written and directed by his friend William Peter Blatty; although he had loved that movie's synopsis, he chose not to direct it due to artistic differences with Blatty, and didn't watch it when Blatty's vision was later compromised by studio interference. Of L'Exorciste II : L'Hérétique (1977), he saw only half an hour, and called it "a stupid mess made by a dumb guy. Scurrilous. A horrible picture. One of the worst films I've ever seen, [..] made by a demented mind."
It was briefly rumored during production that William Friedkin was involved with this film. Friedkin immediately tweeted, "That's not a rumor, that's a lie." He further elaborated there was "not enough money or motivation in the world" to make him work on the film in any capacity.