* AdaptationDisplacement: The number of people who've seen the movies dwarf the number who've read the book quite handily.
* AlternativeCharacterInterpretation: There's some room for uncertainty regarding whether the aliens are truly replacing the originals, and taking their memories is merely useful for blending in, or if they actually see themselves as merging with the original individual in a symbiotic relationship. This can make the aliens either a case of AlwaysChaoticEvil, or simply BlueAndOrangeMorality.
* DeathOfTheAuthor: There's a noticeable divide among film critics and historians over whether the original film is an allegory for Communist takeover or the insular paranoia of [=McCarthyism=], both of which were fears of the American public at the time the film was made.
* HarsherInHindsight: The original novel, the 1956 and 1978 films have been seen as allegories of communist takeover. While the future is current a ways off from the global takeover depicted in the film and novel, [[WhatDoYouMeanItsNotPolitical and the communism angle is one of several put forth for the film]], the idea of communist takeover was a reality when they were written since [[UsefulNote/ColdWar The Cold War]] was taking place, UsefulNotes/MaoZedong was in power in China and [[{{UsefulNotes/NorthKorea}} Kim Il-Sung was laying the groundwork for the tyrannical Kim Dynasty and the political ideology of Juche]]. Future events reinforcing this idea include [[{{UsefulNotes/Cambodia}} Pol Pot rising to power and forming the Khmer Rouge in 1963]], UsefulNotes/FidelCastro forming the Communist Party of Cuba in 1965, the fact that Kim Il-Sung's communism-derived Juche ideology has lasted into the 21st century and [[RuleOfCautiousEditingJudgement increasing communist sympathies]] ([[InsistentTerminology often called socialism]]) [[RuleOfCautiousEditingJudgement in Western society in the 1990's - 2000's]].
* ParanoiaFuel: Have your friends and loved ones been acting strangely lately? ''How strangely?'' By the way, if you fall asleep you might be replaced by an alien doppelganger. FYI.
* UncannyValley: In universe as well, at least in the original. The duplicates look like, sound like, act like and have all the memories of the original, but their close relatives know ''something'' is wrong.
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