It’s not the physical world, but the setup and relationships that really hang together well in the movie Forbidden Planet. The basic setup is that Prof*. Edward Morbius on Altair IV is Duke Prospero on his Fortunate Isle from Shakespeare’s The Tempest, as the screenwriters have admitted. He lives there with his daughter Altaira (who is like Miranda) and his robot Robby (The stand-in for the Tempest’s Ariel) Morbius is a philologist, but he lives in a virtual paradise because he’s sitting atop the Krell power plant and has imbibed enough Krell knowledge to build Robby, among other things.
Robby can speak multiple languages and their dialects. Why? Answer – Morbius is a philologist, and he’s been virtually alone since his wife died. While Altairas was growing up, he had to do something. I could see him teaching Robby all those languages, if only to have someone to talk to.
Robby is a robot, not a metal person – not only does he obey Asimov’s Three Laws of Robotics (something actually used to drive home a point near the end of the film), but he has no emotions. His character makes for humorous moments when his purely mechanical reactions produce a simulation of emotion or humanm response, as when, after pouring the remainder of Cookie’s “Rocket Bourbon”, some of it bubbles up as a “burp”. Ropbby’s occasional lapses into wit can be explained the same way, imagining Morbius to have programmed in a set of broad rules for such occasions. (“Nice planet you’ve got here. High Oxygen content.” “I rarely use it myself, sir. It promotes rust.”)
Robby has an Emergency Override! “Emergency Cancellation Archimedes” Appropriate choice of codeword, too.
Altair IV seems to physically be too deserty, like Arrakis – the terrain we see the spaceship C57D pass over seems to be nothing but desert, and the ship lands in barren territory (although one of the crew remarks that “It’s out there in the desert!”). We only see forested areas around Morbius’ house. But there’s nothing to say that there aren’t other non-barren areas. Morbius’ statements about the wildlife – the deer and birds – seems to indicate that this is the case. And nothing requires that Altair IV, like Arrakis, be a virtually complete desert.
The novelization of Forbidden Planet by “W.J. Stuart” (actually mystery novelist and screenwriter Philip MacDonald) takes liberties with the screenplay and suggests that much of, if not all of, the animal and plant life of Morbius’ world is artificial creation. A monkey run over by the transport has nonsensical anatomy, when Doc Ostrow dissects it. In that case, Morbius has been fooling himself, and the animals weren’t brought to Altair IV by the Krel. This seems a pretty radical departure to me.