Intelligent aliens feature in 17 out of the 29 episodes in the first season of Lost in Space. Two, however, have no physical form so we never see them. Of the 15 episodes where they appear, eight feature aliens that look, to all intents and purposes, entirely human. The remaining seven episodes depict aliens that are truly alien-looking.
The plots of both “My Friend Mr. Nobody” and “Follow the Leader” turn on the interaction between members of the Robinson family and two beings. In the former episode, Penny gives this creature the whimsical name Mr. Nobody and develops a close relationship of mutual affection. In the latter, John Robinson’s mind is taken over by the spirit of one Canto, a deceased military leader who plans to use John to continue his conquest of the universe. Canto’s mask, which John wears near the end of the episode, suggests that in life Canto must have been very human-looking, although we do no know what colour he may have been—and in subsequent seasons we encounter aliens who are very humanlike, but green or purple in colour.
Although entirely human-looking aliens visit Priplanus eight times during the first season (and in the first episode of season two), they are usually proven to be not very human in their outlook and ethics. The Keeper (in “The Keeper: Part 1 and 2”) shows no qualms over imprisoning and exhibiting other sentient beings. The trader in “The Space Trader” similarly feels no moral dilemma over selling Dr. Smith, and uses the technology at his disposal in an attempt to force the Robinsons into buying his wares. Sibylla’s family (in “The Space Croppers”) show entirely unconcerned that their crop will destroy the Robinsons. The race encountered in “The Lost Civilization,” while superficially quite like us, are another example of a people out to conquer the universe. The Tauron family (“The Sky Is Falling”), the boy behind the mirror (“The Magic Mirror”), Quano and his father (“The Challenge”), and both Ohan and Bolix (“All That Glitters”) are perhaps the most human-like of all the aliens encountered in the first season, both in looks and in character. Even if their somewhat different agendas serve as the catalyst to drive forward the plot of the episodes in which they appear, none of these races is categorically evil, or even simply callous, towards the Robinsons.
The final type of aliens seen over the first season are those who are truly different from us. Communication is not apparently possible with the bubble creatures in “The Derelicts.” Although they are not hostile (they were in suspended animation when the Jupiter 2 lands in their ship, as we find out in an episode from season 2), they defend themselves after being attacked; this is not an unreasonable response, when you think of it. The “Invaders from the Fifth Dimension” and the otherwise unidentified alien to whom the robotoid clandestinely reports in “War of the Robots” are both scary looking as well as malevolent, although, to be fair, the Invaders might better be classified as simply callous. The mummy-like creature in “Wish upon a Star” works from a motivation that is not entirely clear to us, beyond him wanting to reclaim the wish-granting helmet; he is not truly menacing, though frightful in appearance. The blob-like alien that pursues Alonzo P. Tucker in “The Space Pirate” is downright virtuous; he is on a mission to obtain what was stolen from his planet by that scoundrel Tucker. In his own somewhat unique way (and very similar to Quano and his father) the Andronican in “His Majesty Smith” behaves in accordance with his own clearly defined code of ethics (and incidentally gets rid of a number of otherwise useless individuals in the process—less ethical, by our standards). Similarly, it is quite understandable why the alien in “A Change of Space” is furious to discover that his second vehicle, which he’d left parked in a very safe location (you can’t get much safer that parking in the middle of a bunch of quicksand pits), has been stolen and taken for a joy-ride twice by alien punks (Will and Dr. Smith). It is actually much to his credit that he eventually restores Dr. Smith to his former self after his grand-theft auto adventure has very adverse effects on him.
The sapient intelligent species encountered by the Robinsons in season one come in all shapes and stripes. Most are not even evil, despite the old cliché about aliens. In fact, the many of these encounters could have had a distinctly more pacific outcome had the humans (usually Dr. Smith) not bunged things up so badly at the outset.