To me as a child watching Lost in Space the difference between a robot and an android was clear. Robots were made of metal (mostly), clunky, and, well, er, robotic. Androids, on the other hand, looked like people with silver skin (usually), had the smooth movements of people, and were generally just more impressive than robots (sorry, Robot).
The crew of the Jupiter 2 first encounter androids in the season one episode “His Majesty Smith.” Nexus and the rest of Dr. Smith’s court were clearly identified as androids, and we are led to believe that the Daddy Zack replacement provided for Dr. Smith by the Andronican Master was an android too. Daddy Zack is one of the few androids we meet who isn’t silver.
Androids appear in at least three episodes in season two, and possibly a further two. In “The Android Machine” and “Revolt of the Androids” we meet Verda, and see her well on her way to her transformation into a human being, or at least a more human-like appearance and emotional life. “Revolt” ends with her moving off to an isolated planet with Idak Alpha 12, another android, to begin a new life together. Raddion in “The Dream Monster” is identified as an android (he’s actually gold, not silver). His creator’s mission for him is to acquire human emotions.
“The Ghost Planet” features a robot in charge of what are apparently androids, although from their rather awkward movements, they might just as well be robots. The creations featured in “The Phantom Family” as replacements for the Robinsons were created out of cosmic dust; if they are not androids, then they must be relegated to the status of experimental creations, although I don’t see why one couldn’t use cosmic dust to make an android (in for a penny, in for a pound).
In season three’s “Kidnapped in Space” we meet a whole civilisation of androids who exist to serve their master computer. We are are safer ground here because they are silver. They also have the ability to download programming (in this episode, knowledge of the English language) from their computer.
“The Space Destructors” features some rather pasty attempts by Dr. Smith to create his own army of androids to do his bidding. He eventually settles on his own likeness as the most perfect model for his androids. This is the episode where Will is incorporated into a Mini-Me android clone of Dr. Smith, by the way. Actually, wouldn’t that make Will a cyborg?
“The Space Destructors” features an evil robot who seduces our Robot, but the law enforcement official is accompanied by what are called “mechanical men." Given that they are silver and don’t have much personality, they might just be androids.
Putting all the pieces together, perhaps we can arrive at a better definition of android in Lost in Space than I had as a ten year old: an android is (a) an artefact created (b) with a definite and exact humanoid body plan (c) that nonetheless has intellectual and physical capabilities enhanced by its mechanical nature.