"There are some corners of the universe which have bred the most terrible things. Things which act against everything we believe in. They must be fought."Cybermen on the Moon, as the perennial favourites make their second appearance in essentially a retread of their first.It's 2070 AD and Earth's weather is controlled from a station on the Moon by means of the Graviton. The crew of the station are coming down with a disease that turns out to be a Cyberman-engineered poison. Polly and Ben realise that as Cybermen are part-plastic, solvents ought to harm them, and mix up a cocktail of chemicals which they use in fire extinguishers to defeat the Cybermen on the base.note A second wave of Cybermen invade across the Moon's surface but the Graviton quickly sends them flying off into space and the travelers go on their merry way.Called Doctor Who and the Cybermen in the 1974 novelization.
— The Doctor
- Artistic License – Chemistry: As Doctor Who Magazine later pointed out, Polly's "cocktail" of solvents would end up reacting against each other and turn into a thick brown gunge, totally different from the clear liquid presented in the episode. That issue also guessed that she was throwing any solvent she could at them in the hopes that something would work.
- Continuous Decompression: This episode features the subtrope of characters struggling to seal the hole as the air rushes out. One fan actually did the calculations to see how long it should have actually taken for decompression to happen. The results were something on the order of a few seconds. The scene in the episode lasted much longer, obviously.
- Creepy Monotone: Cybermen's voice turned from bizzare singsong to a fully mechanical voice.
- Digital Destruction: The Region 1 disc was incorrectly mastered at 23.98 progressive fields per second rather than the correct 59.94 interlaced fields per second, which both causes the release to lose its restored videotape look and to play roughly 4% slow.
- Exty Years from Now: Averted, but only just. The story aired 1967, but the episodes were set in 2070.
- Multinational Team: The crew of the Graviton station.
- Nightmare Fuel: In-Universe—Jamie, slipping in and out of consciousness, mistakes an approaching Cyberman for the McCrimmon Piper; given the circumstances, the Piper would be the better option.
- Not Himself: Personnel under cyber-control.
- Not That Kind of Doctor: The Doctor actually claims to have recieved a medical degree...from Joseph Lister in 1888. Polly is ...skeptical about its continued applicability.
- Oh Crap!: The Doctor, followed slowly by everyone else in the room has a rather epic one at the conclusion of one episode when the base leader argues that there can't be any Cybermen in the base because they've searched every single room for them...except the one they're in right now. Guess where the Cyberman turns out to be hiding?
- One Steve Limit: Benoit was originally called Jules but was changed Roger due to another character named Jules.
- This is also why he wears a scarf, his shirt was designed before the name change and has letter J on it and the scarf was used to cover it up(for the most part)
- Resistance Is Futile
- The Siege: Mainly happens in episode 4 when the infiltration of the Moonbase has already been exposed. The Cybermen throw subtlety to the wind and march in force, openly attacking the base.
- Smart Ball: Ben Jackson suddenly has considerable knowledge of chemistry, physics, and medicine that he never displays again.
- Stay in the Kitchen: Ben tries this on Polly. She doesn't listen.
- Tampering with Food and Drink: The Cyberman spike the base's sugar supply as a means of spreading their virus.
- Tap on the Head: Averted. Jamie's bump on the head is treated very seriously and keeps him bedridden for the first two episodes.
- Which actually happened because Jamie wasn't meant to stick around at first, and the writers had to rush to put him in the script.
- True Companions: From the scenes where we see Captain Hobson and Second-In-Command Benoit conversing together, you can see that they care for each other.
- Weaksauce Weakness: After being ridiculously vulnerable to radiation in the previous story, this story has the Cybermen dying unpleasantly if you pour organic solvent over them.
- Weather-Control Machine: The Gravitron, situated on the moon and which controls the weather on the Earth.
- You, Get Me Coffee: The Doctor telling Polly to make some coffee is often used out of context in clip shows as an example of early Doctor Who being sexist. In context, it's a means of distracting Hobson from blaming them for the problems, and it's Polly who later in the story comes up with the idea of attacking the Cybermen with solvents.