Invasion of the Body Snatchers, 1956
As long as I'm doing the RIP event, I may as well tell you about the movie we just watched for the Peril On The Screen portion of the challenge. Invasion of the Body Snatchers is, of course, one of the big classic alien invasion films! I don't think I'd ever actually seen it before, even though I know all about pod people. My daughter and I love Daniel Pinkwater, and he riffs on pod people in Lizard Music, so we both wanted to see it.
In the small town of Santa Mira, a doctor comes back from a conference to find that a) his old girlfriend is back in town and available, and b) several people seem to be hallucinating that their closest relatives are no longer themselves. Soon, he and his true love are on the run from terrifying plant-based aliens who first grow into copies of people, and then take over their minds while they sleep. Can they make it to the outside and warn the world before it's too late??
It's a pretty great movie, despite a little lack of coherence on the takeover process. You'll see some familiar faces from the 50s. Like so many SF stories of that time, it can be seen as a fantasy about the dangers of communism (or maybe brain-washing, or heck, conformity); the pod people lose all humanity, become completely alike, and work together in a hive-mind-esque way. It was re-made in 1978, so I'd quite like to see that; I bet it's entertainingly bad.
Great classic movie.