- Broken Base:
- This episode could be considered the archetype for this trope, given the fan reaction to Missy actually being a female incarnation of the Master, exploding the debate over whether the Doctor should someday be played by a woman. Although the producers have frequently lied about future plans for the series many times before (with Steven Moffat openly stating that this is his modus operandi), some fans have seen this as the last straw. Meanwhile, a huge contingent of fans acclaimed the episode, loved the twist, and felt all was right with the world. Additionally, there are arguments over sexual orientation representation, with some fans viewing it as homophobic that the Master is only allowed to kiss the Doctor when she's a woman, and others viewing it as progressive treatment of Gallifreyan gender ambiguity.
- There's also the debate over whether the Master should have come back at all, given his highly rousing exit in his previous appearance that easily could have stood as his permanent departure from the show.
- A variant of this being fans who wanted John Simm to return as the Master.
- And a third group who wanted Missy to be The Rani (she is the most common Classic series villain brought up when it comes to returning villains) or someone new.
- According to the actors, when the reveal scene was shot in a public place, Gomez was in fact instructed to say she was the Rani in order to throw off any lip-readers in the crowd (the real line was added in post-production combined with a close-up where Gomez was instructed to "mouth" the dialogue without actually saying it. This obviously doesn't apply to close-ups where Gomez clearly said "the Master" on camera.)
- The plot points concerning the dead still being conscious (even though this was a scam perpetrated by Missy) were sufficiently disturbing to enough of the audience that the BBC actually had to issue a press release defending the story. It also triggered a rare re-rating of the episode that resulted in the DVD release of the entire season being delayed.
- Clara's attempt to blackmail the Doctor into saving Danny. For many, this was the final straw and many stated their dislike of Clara for being childish enough to be willing to destroy the TARDIS keys (at least, in her head) over Danny (As was proven in Series 1, this should never be done). Others, meanwhile, felt it greatly expanded on Twelve and Clara's relationship and loved it. The events surrounding the Series 9 finale (in particular, the Doctor executing a variation of what Clara attempted, only cranked up to Twelve, has led to this being seen as one part of a bookend for the characters.
- Ship-to-Ship Combat continued between those loyal to the Danny and Clara ship and Twelve and Clara and ramped up due to the events of this episode. Not helped by Steven Moffat's Word of God confirmation that the Doctor's statement to Clara, "Do you think I care so little for you that betraying me would make a difference" was a Love Confession.
- Captain Obvious Reveal: Missy is the Master.The Doctor: Who are you?
Missy: Oh, you know who I am. I'm Missy.
The Doctor: Who's Missy?
Missy: Please, try to keep up. Short for Mistress. Well, I couldn't very well keep calling myself the Master, now could I?
- Foe Yay: The tension between the Doctor and the Master has never been so explicit.
- Hilarious in Hindsight: Peter Capaldi played a part in a Tear Jerker music video by Lewis Capaldi. His character is a man whose wife died and became a heart donor. The saved woman meets the Peter's character, grabs his hand and presses it against her scar. What do whovians think while watching the video? "Doctor Chaaaang!".
- Ho Yay:
- A bizarre variation involving a Gender Bender with the Master, who has been male in numerous incarnations but now goes all-out in a female body. Said female body also tries to kiss Clara, who sadly refuses. Not entirely out of character for the Master, who has had a Ho Yay-esque relationship with the Doctor since his introduction.
- On Clara's post-it-note Room Full of Crazy (to remind her to tell Danny the whole truth), there are suspiciously focused shots on "Maisie" and "Jenny", both of whom she's flirted with in season eight episodes.
- Memetic Mutation: The phrase "Danny Pink didn't Splink" became a rather popular way to jokingly describe Danny's unceremoniously sudden death in this episode, based on this 1976 road safety PSA starring former Third Doctor Jon Pertwee.
- Shocking Moments: To say that The Reveal of Missy's true identity sent shockwaves through the fandom would be an understatement.
YMMV / Doctor Who S34 E11 "Dark Water"