* EnforcedMethodActing: According to IMDB, in the [[spoiler: 1978]] version, the directors did not tell the actress playing Nancy about the TwistEnding so her shriek of terror when [[spoiler: Matthew points at her and begins to make the pod-scream]] is genuine.
** The 1956 version ends with the cops catching the snatchers in the act, because the studio thought the original ending was too dark.
** The 2007 version had a particularly bad case of this. The original director Oliver Hirschbiegel turned in a cut that was, like the previous versions, a psychological thriller. The studio wanted an action flick however, and hired the Wachowski brothers to refilm the entire third act.
** English actress Dana Wynter plays Becky Driscoll in the original. They got around it in the script by saying the character had just returned to the U.S. after having lived in England for several years.
** Another Englishwoman, Gabrielle Anwar, played the heroine in the 1993 version.
** The 1978 version features [[Series/StarTrekTheOriginalSeries Mr. Spock]] as a sort of Dr. Spock. [[spoiler:And people ''actually'' [[TheStoic noticed that he had been replaced]] by a pod?]]
** [[TheDickVanDykeShow Mel Cooley]] is one of the mental hospital doctors in the prologue/epilogue to the 1956 version.
* NoStuntDouble: Donald Sutherland insisted on this during the film's climax, climbing fifty feet into the air and dodging very real explosions. In fact, one of the explosions barely missed him, but caught an extra who missed his cue and was injured.
* PlayingAgainstType: The 1978 version. We're all used to seeing Leonard Nimoy [[Series/StarTrekTheOriginalSeries without emotions]], but it isn't normally this creepy.
* WhatCouldHaveBeen: Legend has it that the 1956 version originally ended with the hero, Miles Bennell, on the highway screaming "You're next! You're next!" to all the passing motorists, leaving the audience on a cliffhanger, but the studio disliked this ending so it was changed to a more hopeful ending.