The Doctor: Emotions. Love. Pride. Hate. Fear. Have you no emotions, sir?
Cyberman: Come to Mondas and you will have no need of emotions. You will become like us.
This was William Hartnell's last story as the incumbent Doctor, and the debut of Patrick Troughton as the Second Doctor, in the first instance of regeneration on screen. Since this was just an experimental plot element at the time, the actor changeover occurred partway through Season 4, an unusual move that would not be repeated with future actors set to leave the role of the Doctor. Later regenerations would normally not take place until a respective season finale or end-of-year special to cap off that Doctor's tenure. A few of the Doctor's regenerations have been depicted under unique circumstances, when they were sudden plot twists or "past due", so to speak. Regeneration was not an ability exclusive to the Doctor, as it would be explained as a feature of the Doctor's species and demonstrated by others like him as well.Episode 4 is, unfortunately, reduced to audio with stills and scene directions (although footage of the regeneration itself survives). An animated reconstruction of the fourth episode has been produced for the story's DVD release, initially in June 2013 as part of a Limited Special Collector's Ultimate Edition box set of all the Doctor's final stories, and later on its own.
- Accent Upon The Wrong Syllable: Theeee CYbermen have A biZARRE singSONG ACcent.
- Air-Vent Passageway. Used by Ben to get to the missile to sabotage it. According to the DVD commentary, the first example in the history of Doctor Who.
- All Your Base Are Belong to Us: Twice at Snowcap, and at the space agency HQ and reportedly other major government and military sites in the final episode.
- Apocalypse How: Somewhere between Classes 4 and X, according to the Cybermen, although the Cybermen offer to rescue what humans they can as long as they accept Cyberconversion once they get to Mondas. Mondas itself suffers a Class X at the conclusion of the story.
- Artistic License - Astronomy: Exactly how the Z-Bomb would make Mondas explode like a supernova is never explained, nor is there any major gravitational effect on the Earth from a planet of equal size coming close enough to distort the orbits of spacecraft in low earth orbit, or how the disintegration of said planet left the Earth unaffected.
- Benched Hero: Happens to William Hartnell frequently during the third season, but it is especially apparent here. The Doctor is absent entirely from episode 3 due to Hartnell's health that week, and even in the episodes where he appears his role is much reduced as he sits on the sidelines for much of the story, held prisoner either by the Cybermen or by General Cutler.
- Black Dude Dies First: Unbuilt Trope. Though the astronaut played by black actor Earl Cameron does die halfway through episode two, he's not the first to go. The Sarge and Tito die first, killed by the Cybermen at the end of episode 1 and the beginning of episode 2 respectively. Normally this would be an aversion, but the trope had yet to actually be established.
- Body Horror: The point of the Cybermen's cloth faces and bare arms.
- Chest Blaster: Actually a gun kept on a chest bracket when not it use. And a bit lower than the chest, which sometimes leads to unintentional humour.
- Creepy Monotone: Quasi-example — the Cybermen talk in bizarre, alternating, almost singsong tones which nonetheless carry no emotion.
- Culture Clash: The Cybermen genuinely don't understand why the Humans don't wish to cooperate with their plans.
- Earth-Shattering Kaboom: The major threat for both planets during the final two episodes.
- Exty Years from Now
- Fake Shemp: The "Doctor passes out at the start of an episode for no clearly explained reason" plot device gets one last outing at the start of Episode 3. William Hartnell collapsed with bronchitis and had to take a week off. As a result, Hartnell's regular body double Gordon Craig plays the Doctor for Episode 3, and the lines originally written for the Doctor were given to Ben, Polly and Barclay. Craig also doubles for Hartnell in the "exterior" scenes in episode 1 as the TARDIS crew are arrested and taken into the base.
- Hartnell's absence for Episode 3 actually works in the story's favor, as it means the Doctor summoned enough energy for a "once more unto the breach" and you can tell he's dying as Episode 4 progresses.
- Five Rounds Rapid: Averted! The Cybermen are Immune to Bullets, but the Snowcap personnel quickly manage to get hold of some Cyberguns, which work perfectly well. Played straight, however, with Cutler's death.
- General Ripper: General Cutler.
- Getting Crap Past the Radar: The photos from girly mags (some very revealing by sixties standards) glued up by Tito's bunk.
- Multinational Team: At both Snowcap and the space agency headquarters.
- My God, What Have I Done?: Ben after he kills a Cyberman in self-defence.
- National Stereotypes: The Italian soldier has pin-up photos all over his bunk and perves over Polly, and the American General is a trigger-happy nut.
- No Ontological Inertia: Played with: the Cybermen draw power from Mondas, thus it makes sense that its destruction means their death. But rather than simply falling down dead when Mondas is destroyed, their organic parts out-and-out disintegrate.
- The Nth Doctor: The first notable example.
- Nuke 'em: Cutler's plan in Episode 3, despite what would have been catastrophic results for Earth.
- Sheathe Your Sword: Mondas blows up on its own, killing all the Cybermen, and Cutler's attempts to take more aggressive action would have led only to disaster.
- Stay in the Kitchen: The space program has men from all over the world (as opposed to a purely American or British program) but no women whatsoever.
- Tempting Fate: The news broadcast reporting that there is absolutely no danger from the mysterious new planet.
- Thicker Than Water: Cutler's more irresponsible actions are driven by the desire to save his son.
- Villainous Rescue: Cutler is on the point of murdering the Doctor and friends when the second Cyberman squad burst into the base and kill him. The Doctor is generous enough to thank them. Also a big part of their plans for the people of Earth, for a given value of "rescue."
- Weaksauce Weakness: These Cybermen are much more vulnerable than humans to radiation, despite their bionics.
- Well-Intentioned Extremist: How the Cybermen got the way they are.
- What Measure Is a Non-Human?: Averted: the Cybermen here uniquely have individual names, and Ben feels guilty after killing one of them in self-defence.
- Wham Episode: Introduction of the Cybermen, regeneration debuts, Hartnell leaves.
- Wham Line: A Cyberman to Polly: "There are millions of people dying all over your planet, but you do not "care" about them."
- Wham Shot: The final moments of episode 4, in which the Doctor regenerates for the first time.
- You Can't Fight Fate: The first time that this trope is applied to something that the Doctor evidently knows as being a historical fact, but which is still in the "future" of the viewers watching at home. Once he recognizes where he is and what's going on, the Doctor subsequently treats all events in the episode as being inevitable.