Trivia: In the scene where Regan's mother is supernaturally blasted away from the bedside, she is being yanked by the crew by a length of rope. After dozens of takes director William Friedkin was still unhappy with the look of the shot and ordered the crew to haul her more fiercely. The scream in the shot that made the cut was of genuine pain and required no dubbing for effect.
Trivia: When Terry is being introduced, he drives up on his scooter, and has quite a bit of trouble parking it. This is because Charles Martin Smith actually didn't know how to drive a stick shift. The small accident he has is real, you can see him crash, look up towards the camera (at Lucas), and continue the scene. Lucas motioned for him to continue, because the crash looked so interesting.
Trivia: The weapons used against Megalon (the ones that look like satellite dishes that shoot lightning) actually existed, although they were never used in combat. The Japanese experimented with them during WWII.
Trivia: Yul Brynner, The Man in Black, has only 9 lines of dialogue throughout the movie, only 32 words. In the first saloon scene, Brynner intentionally bumps Richard Benjamin and says, "Sloppy with your drink"; after some silence, Brynner says to the bartender, "Get this boy a bib"; a few moments later, Brynner taunts again, "He needs his momma"; Benjamin finally summons the courage to speak, and Brynner replies, "You say something, boy?" Benjamin says Brynner talks too much, and Brynner challenges, "Why don't you make me shut up?" Whereupon, the two men square off for a duel, and Brynner finally says, "Your move." Later, about half-way through the film, when the Man in Black invades their hotel room, Richard Benjamin overhears Yul Brynner say the line "Not a word" to James Brolin. Even later, Brynner challenges Benjamin and Brolin in the street: Brynner first says, "Hold it," and shoots Brolin dead; Brynner then smiles at Benjamin and says, "Draw."
Trivia: Despite repeated citations in print, (as recently as the 2001 edition of 'Film Facts' by Patrick Robertson), both Donald Sutherland and Julie Christie maintain that the sex scene between them was, in fact simulated, and they did not actually have sex, as has been widely reported.