Debuting way back in 1951, the film is about an alien, named Klaatu, and his big clunky robot, Gort, who land their spaceship in the middle of Washington D.C. with the intention of delivering an important message to the world. Humanity gets off on the wrong foot by shooting him, and eventually Klaatu ends up on the run from the U.S. military while he tries to find a way to communicating with the planet.
Klaatu is portrayed as an affable and friendly alien, while the majority of humans we see in the film are paranoid and suspicious of his intentions. It is, of course, an allegory for the Cold War, where people's hostilities are overriding both their common sense and their common humanity. Klaatu is less than impressed by how he's being treated, but he still tries to see the best in Earth. Even when he demonstrates how powerful he is, he does it without killing anyone, and it's only after the poor guy eventually gets gunned down does his robot buddy get angry.