- Author Existence Failure: Originally, the script had a major role for Lt. Kinderman from the first film, but upon Lee J. Cobb's death the entire film was reworked.
- Awesome, Dear Boy: Apparently, the initial script was fascinating enough to make Linda Blair sign up for it. The results were different, though.
- B-Team Sequel: Neither William Friedkin nor William Peter Blatty returned for the sequel.
- Big Name Fan: One of the film's few defenders was Martin Scorsese, who asserted:"The picture asks: Does great goodness bring upon itself great evil? This goes back to the Book of Job; it's God testing the good. In this sense, Regan (Linda Blair) is a modern-day saint like Ingrid Bergman in Europa '51, and in a way, like Charlie in Mean Streets. I like the first Exorcist, because of the Catholic guilt I have, and because it scared the hell out of me; but The Heretic surpasses it. Maybe Boorman failed to execute the material, but the movie still deserved better than it got."
- Creator Backlash: Linda Blair thoroughly enjoyed William Goodhart's original script, and signed on to the film because of it. During production, Blair claims, the script was re-written five times or so, and she was very disappointed with the final results.
- Cut Song: While "Magic and Ecstasy" is featured in the trailers, it wound out of the picture - re-edits put it as credits music.
- Enforced Method Acting: John Boorman filmed the scene on Regan's balcony, which isn't a set, knowing full well he had no way of catching her if she fell. Her screams of fear are real.
- Flashback with the Other Darrin: Blair agreed to reprise her role of Regan MacNeil under the condition that she wouldn't wear the demon make-up, so a double was used for the brief flashback scenes depicting a demonic Regan.
- Hire the Critic: As noted below, John Boorman openly detested the original Exorcist, and it's been argued that he did the exact opposite of everything that worked in the original or would have made sense as a continuation of the story. Ironically, even Boorman himself was disappointed with the resultant film.
- Keep Circulating the Tapes: The re-edited version is only available on VHS. The Shout Factory Blu-Ray, expected to be released in the summer of 2018, will include both versions.
- Old Shame: For both director John Boorman and Linda Blair, Blair even going as far as calling it "one of the big disappointments of my career."
- One for the Money; One for the Art:
- Troubled Production:
- William Friedkin and writer William Peter Blatty were repeatedly asked for ideas for a sequel, but they turned the studio down on finding out that the producer assigned the project, Richard Lederer, wanted them to just make a quick-and-dirty sequel to exploit the first film's success. After their refusal, the studio commissioned a screenplay by William Goodhart, whose only other screenplay credit was the obscure 1969 film Generation. The exact contents of Goodhart's screenplay have never been made publicly known, but it apparently mixed in the first film's themes with a lot of odd metaphysical symbolism.
- The studio then hired John Boorman to direct the film an odd choice when you consider that he actually disliked the first film, and was more interested in the metaphysical aspects of Goodhart's script than any of the actual Christian themes. Boorman and co-writer Rospo Pallenberg then pretty much scrubbed all the remaining Christian elements from the script, leaving it barely recognisable as an Exorcist sequel. They then hard to perform further last-minute rewrites which swapped out Regan's mother Chris for Sharon, the nanny from the first film, after Ellen Burstyn refused any notion of appearing as Chris again.
- Filming was where things really started to go wrong. The production was refused permission to film at just about every location they asked for (including the house from the first film), leading to them having to recreate everything on the studio backlot and inflating the $9,000,000 budget all the way up to $14,000,000. Linda Blair was already in the midst of her drug habits and constantly turned up late to shooting, to the point where she actually considered it an achievement that she was only 20 minutes late one day. Co-star Richard Burton had his own substance issues, as he was constantly drunk on set and frequently lashed out at Boorman and his co-stars. Boorman was also laid low by a serious lung infection for a month, resulting in Pallenberg who had never directed a film before taking over as director for many key sequences. The crew also had no idea how to realize the swarms of locusts that were required for the climax, resulting in them using a combination of styrofoam "packing peanuts" fired from an air cannon and actual locusts with their legs clipped, with mixed results. On top of that, the locusts could only survive for a day or two in the American climes, so they had to be constantly replaced at considerable cost.
- When the film was finally released, it was laughed off the screen during its premiere, leading to Boorman hastily producing a re-edited version, which was no better received. The studio had desperately granted Boorman to do the final cut of the movie without any kind of studio oversight, but the result was considered such a disaster that no major studio has allowed that since for any movie.
- What Could Have Been:
- William O'Malley was contacted to reprise his role as Father Joseph Dyer from the first film. However, O'Malley was busy and could not take up the part, and the character of Father Dyer was changed to Father Philip Lamont. David Carradine, Jack Nicholson, Jon Voight and Christopher Walken all were considered or offered the part of Father Lamont, who John Boorman initially conceived as a younger priest in awe of Father Merrin's writings. Eventually the choice was made to age the character, and Richard Burton was signed for the role.
- Stanley Kubrick turned down the offer to direct. When John Boorman accepted, Kubrick warned him that the only way a sequel to The Exorcist would succeed is if it were to be more graphic and horrific than the original.
- When the role of Dr. Tuskin was still written as male, Alan Arkin, Carraidne, Richard Dreyfuss, Chris Sarandon, Martin Sheen and Gene Wilder were considered.
- Jane Fonda was considered for Dr. Tuskin.
- Louise Fletcher was originally considered for Chris MacNeil when the role was still in the script, as Ellen Burstyn repeatedly turned down offers to reprise the role. Ultimately, Chris's role was given to Sharon Spencer after Kitty Winn agreed to return, and Fletcher was assigned to play Dr. Tuskin after no suitable male actor could be found.
Trivia / Exorcist II: The Heretic