Trivia: When Doc Terminus is tied to the harpoon shot from the cannon and goes through the building roof, you can hear a "Goofy Holler."
Trivia: David Lynch has never explained how the disturbing "baby" was created for the film, even coyly suggesting at one point that it was something he found that had been "born nearby." A popular theory is that the baby is actually an animal fetus that had been hollowed out and made into a puppet, but this has never been confirmed.
Trivia: Director John Boorman initially didn't want to make the movie as he found the first film distasteful. However, when he saw the story treatment, his perspective changed and he viewed "Exorcist II" as a rebuttal to his perception of the original film's darkness and a tale about "goodness" winning. Boorman subsequently admitted that his views were wrong and that the movie didn't work, and that he shouldn't have made it since he "denied what the audience wanted."