Looking up something about the movie The Day The Earth Stood Still, I accidentally discovered that the movie was based on a short story by a writer named Harry Bates called Farewell To the Master. It was originally published in the October 1940 issue of Astounding Science Fiction and its plot is rather different from the movie.
There’s a detailed summary on the Wikipedia page, but the short short version is that a man and robot emerge from a space ship, Klaatu and Gnut, a lunatic shoots Klaatu who dies and is buried in a mausoleum, the robot stands still for a few days, then eventually retrieves Klaatu’s body and leaves, intending to make a new Klaatu.
As the robot prepares to depart, Sutherland impresses upon it the need to tell its master, the Klaatu yet to come, that his death was a terrible accident. Gnut replies, “You misunderstand, I am the master.”
In the movie, the robot Gort is very much a servant, if an autonomous servant. It was created by the peoples of the galaxy to ensure peace (by wiping out anyone sufficiently warlike). I wonder how it was the movie came to be based upon the short story. It only has a few things in common.
Chris Lansdown 
I suspect that the movie script wasn’t actually based on the Short Story but there was enough in the movie script that reflects the Short Story that the movie makers believed that they had to say “based on the short story”.
Harlan Ellison believed that the movie “Alien” was based on one of his stories and won a law suit over it.
The Movie Makers may not have intended “Alien” to be based on Ellison’s story, but Ellison made a case for it.
Earlier Robert Heinlein sued a movie maker for using the plot of his Puppet Masters in a B-Movie. (Forget the movie’s name but it wasn’t titled The Puppet Masters.)
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Good point.
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The Movie I thought of was called “The Brain Eaters”.
https://en.wikipedia.org/wiki/The_Brain_Eaters
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By the way, I was mistaken about Ellison and “Alien” movie.
There was a similar alien in A. E. van Vogt’s “Voyage Of The Space Beagle” but van Vogt’s law-suit was settled out of court.
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Bluntly, to avert other claims of copyright infringement.
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Fair point.
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