* AlternateCharacterInterpretation: The ending of the book is ambiguous: either Richard [[spoiler: decided to return to London Below and went with the Marquis]] or [[spoiler: the whole thing drove him kind of insane and he just imagined that happening because he couldn't deal with London Above anymore]]. Given how Gaiman tends to avoid that kind of twists, it's still probably the [[spoiler: former]]. [[TakeAThirdOption Although it could be both.]]
* AuthorAvatar: Possibly. Read the physical description of Richard Mayhew. Then take a look at Neil Gaiman's author portrait.
** Jossed on Gaiman's tumblr. He described Richard based off the original actor from the TV show.
* CompleteMonster: Croup and Vandemar. [[spoiler:And Islington. Hell, even Croup thinks Islington]] has "travelled so far beyond right and wrong he couldn't see them through a telescope on a nice clear night."
* LesYay: Hunter and Serpentine are implied to have been lovers in the past - a time apparently remembered fondly by both women.
* MagnificentBastard: The Marquis de Carabas would be one of the defining examples.
* MoralEventHorizon: See VillainousBreakdown on the main page. Also explicitly stated by Croup - "He's travelled so far beyond right and wrong he couldn't see them through a telescope on a nice clear night."
* NightmareFuel: NeilGaiman the NightmareFuelStationAttendant strikes again. Croup and Vandemar in particular.
** The fate of [[spoiler: poor little Anaesthesia]] comes to mind. Although, oddly, [[spoiler: the possibility she may return someday]] is discussed.
** Richard's Ordeal of the Key. [[spoiler: Made even worse if you are a supporter of the "Richard is insane" theory]].
* SpecialEffectsFailure: The miniseries' Beast of London bears a striking resemblance to a cow with a fur rug thrown over it.
* UncannyValley: In the TV adaptation [[spoiler: Islington's eyes are covered with black contact lenses.]] When you first see his face you can see something is ever so slightly wrong with it, but it's difficult to tell what. It's made very obvious after TheReveal though.
** For that matter, Door and the Marquis (''especially'' the Marquis) in the comic book adaptation. His skin is literally ink-black and the only visible parts of his face are his eyes and mouth.
* TheWoobie: Anesthesia. She never had a father, her mother went insane, and she was raped by her aunt's boyfriend. On her eleventh birthday, she told the aunt, who didn't believe her. She ran away and wound up in London Below. [[spoiler: Eventually, the dark took her.]]