Alien races appear in 25 out of 30 episodes in season two of Lost in Space, a higher proportion of episodes than in either seasons one or three. If one includes non-organic aliens such as androids and robots (I don’t; I am an organo-chauvinist), then the total would be 28 episodes. In fact, “Trip Through the Robot” and “The Astral Traveller” are the only two episodes in the second season that do not include some form of alien life (I am not counting the ghost in “The Astral Traveller” nor his uncle as aliens, for the obvious reason—they were both born on Earth). In two episodes only, “Curse of Cousin Smith” and “Cave of the Wizards,” the alien presence is either only heard (“Curse”) or implied (“Cave”).
The aliens encountered in this season can be categorised as follows. First, there is the individual alien who poses some threat to the Robinsons either directly or indirectly. Nerim in “Blast Off into Space,” Athena in “Wild Adventure” and “The Girl from the Green Dimension,” and Tiabo in “The Forbidden World” are such. Mr. Zumdish (and his hired muscle cum elevator boy) might also fall into this category.
In both “The Golden Man” and “The Galaxy Gift” the Robinsons are caught in the middle of conflicts between two other aliens, forming a second type of encounter. In both of these episodes, much of the dramatic tension is caused by the question of which side, if either, the Robinsons should support.
The third type, outright conflict with aliens, drives the plot in “Wreck of the Robot” and “The Colonists.” In both of these episodes, the crew of the Jupiter 2 are initially overwhelmed by the aliens, but manage to save themselves in the end.The fourth category is comprised of individual aliens with whom the Robinsons come into conflict, knowingly or unknowingly. The episodes in which this is the central plot device are “The Dream Monster,” “Rocket to Earth,” “Space Circus,” and “The Phantom Family.” The aliens in each of these episodes each seek to accomplish their own ends using some or all of the Robinsons; obviously, the Robinsons don’t take that sitting down. “The Prisoners of Space” could be placed here, although the aliens on the tribunal are not malign; similarly, “The Deadly Games of Gamma 6” revolves around deceit and trickery, where Mykos is trying to take advantage of Dr. Smith and John Robinson, and vice versa.The fifth category is a bit of a grab-bag, and consists of those episodes where the aliens are really just silly. That is not to say that they do not necessarily present some element of menace (how else would you get dramatic conflict in the episodes?). Indeed, Dr. Smith under the pendulum blade in “The Thief from Outer Space” and O.M. seeking to sell Dr. Smith and Will as toys in “The Toymaker” are both rather chilling images.
The other episodes in this category are “West of Mars,” “A Visit to Hades,” “The Questing Beast,” “Mutiny in Space,” “The Space Vikings,” and “The Treasure of the Lost Planet.” Episodes in Category five, particularly those just named, can be characterised as “rollicking adventure,” or, if you prefer, high camp.