This is not an easy movie to objectively assess. It was released in the days when most sci-fi films were B-movies. Coming out 3 years before The Twilight Zone, I don't think there's a single scene with production values high enough to allow an otherwise ignorant viewer to determine that it was from a theatrical release, rather than a work of Rod Serling.
My personal view is that this movie hit a cultural nerve because of the time it was released. Much of the population saw this movie as a commentary on Communism. Still others saw it as satirical, sarcastically mocking McCarthyism and the Red Scare, with the suggestion that good law-abiding American citizens were going to sleep one night, and evil Communists were waking up the next day. That does indeed appear to be all that the original is remembered for. Personally, I find this to be a bit of a stretch. The film was neither the first nor last to suggest that inhuman monsters looked exactly like normal people.
The setup for the film is that Miles Bennell (Kevin McCarthy), a Doctor, has been called back early to his small town practice from a conference, due to a large build-up of patients. When he arrives, however, they all mysteriously cancel their appointments. He and his former lover (Dana Wynter) then begin to hear reports of citizens claiming their loved ones have been replaced by impostors. It gradually becomes clear that this is in fact the case. Duplicates of the originals are being grown in mysterious pods, which then absorb the memories of the originals, replacing them.
What I find interesting about the film is the creatures themselves. In most films about humans being assimilated into a collective there are scenes that establish the assimilated as monsters. This film doesn't seem to have that. While they try to prevent the protagonists from leaving town, the Pod People never seem hateful or malicious. In fact, they try to negotiate the humans into surrender. To me, this suggests that they don't see themselves as invaders, but as symbiotic. By absorbing the memories, they believe that the original human lives on. In this sense, the conflict is of two creatures with fundamentally different ways of thinking: Collectivism vs. Individuality (I'm not saying the Communism metaphor doesn't work, by any means. It’s just that I doubt it was intended.).
The obvious comparison to this movie is The Thing. Both films deal with aliens replacing humans, and are based on two separate works on literature that have both been adapted multiple times in film. The major difference that gives The Thing a definitive edge is that John Carpenter knew the real horror of assimilation was complete uncertainty in regards to who is friend or foe. That's the great weakness of this movie. While that element is used in passing, we come to understand that the aliens cannot mimic the personalities of the original perfectly, thus anyone who knows the original well will be able to distinguish an impostor with fairly little effort. So, once the villains are established, there's little real effort to keep their identities secretive.
One thing I have to give the writers credit for is that the book-ends of the film, forced on by the studio at the last possible second, do not weaken it. In the original ending Bennell, the last unassimilated person in the town, makes it to the Highway, but no one is willing to pick up the crazy guy ranting about aliens, let alone believe him. The film would then have closed on him looking at the camera, and telling the audience that they were next.
The studio felt this ending was too depressing. And so instead, scenes were added to the beginning and end, showing that Bennell was picked up by the government and told them his story. The government initially assumes that he is crazy, but then found out about pods being shipped from the town. This was actually a fairly good choice. Because rather than ending on clear defeat or victory, the movie ends with uncertainty, and it works.
I recommend this movie about as strongly as I would recommend a really good episode of The Twilight Zone. It's certainly not a film anyone needs to rush out to see. But likewise, I can't imagine anyone demanding that the sparse 80 minutes of their lives be refunded to them. It's not like the film is hard to find.
