History Literature / TheCustardProtocol

* AsiansLoveTea: Being consummate examples of BritsLoveTea themselves, the protagonists comment on and approve of Asian tea cultures. While most Asian cultures get some mention, the standout examples are India and Japan.

* InconvenientAttraction: Primrose is very dedicated to becoming a ProperLady, including a husband and children, so she absolutely refuses to acknowledge her growing feelings for Tasherit. It gets to the point where even [[NotGoodWithPeople Percy]] calls her on it.

* FantasticFoxes: ''Reticence'' introduces kitsune. They have more distinctly "magical" abilities than other werebeasts, such as a form of mesmerism and illusion that befuddles their targets, and are tied to an Alpha. The Alpha gets sick if she's kept from them too long, while her pack becomes [[FoulFox more conniving, treacherous, and prone to meddling]] without her, leading them to cause political chaos and stir up xenophobia in Japan. There's also a character who is a huli jing, a Chinese werefox, just passing through.

* OfCorsetHurts: Downplayed in that they don't hurt, but are restrictive. Rue starts to go without corsets or stays due to the need to transform at any time, and Primrose envies her her freedom of movement.

* WhoNamesTheirKidDude: Preshea Buss is an infamous BlackWidow and assassin who has killed three husbands and thus finds it delightfully ironic to name her daughters after poisons. At least one is named the (somewhat) acceptable Belladonna, but the last in line (and the one we meet) got stuck with ''Arsenic''.

** Japan introduces fox shifters, who are abnormally light and small and have a form of mesmerism. Japanese kitsune are tied to their clans (and having an alpha away from her clan for too long will make both sick), while Chinese huli jing are independent. [[spoiler:There's also were''dragons'', who can mate with werefoxes and control water.]]

* ShapeshifterBaggage: Established in the second book, where Percy's experiences with the weremonkeys and werelions lead him to conclude this. Tasherit is noted to be a lot heavier in her human form than she should be, and the same applies to werewolves. It's why Percy waves off rumors of weregoats and werefoxes, since they're too small to fit a human form. On the flip side, [[spoiler:kitsune are barely bigger than children and far lighter than they should be.]]

* MayflyDecemberRomance: Being thousands of years old, Tasherit has outlived many mortal lovers, and is ready to start again [[spoiler:with Primrose]]. When she and Lord Akeldama meet up, they fondly reminisce about a man they both loved and a daughter born of their triad.
* TheNondescript: The "Wallflower", a spy so good at this she's managed to hide in ''[[ExaggeratedTrope Japan]]''. [[spoiler:Turns out she's none other than Agatha Woosnoos.]]

* TheNondescript: The "Wallflower", a spy so good at this she's managed to hide in ''[[UpToEleven Japan]]''. [[spoiler:Turns out she's none other than Agatha Woosnoos.]]

** He, Tasherit, and a third preternatural were in a three-way relationship that ended in the birth of [[spoiled:Zenobia, the first metanatural]].

* AbandonShip: Near the end of ''Reticence'', [[spoiler:Lady Sakura has been retrieved, and Edo is drifting away. Because the women Edo were only there to care for her, they leap off and parachute to Tokyo en masse.]]

* BeethovenWasAnAlienSpy: Lord Akeldama is quite casually revealed to be [[spoiler:Alexander the Great]].

* OurWerebeastsAreDifferent: Rue grew up thinking that werewolves were the only type of shapeshifter, but her travels show her that there are many the world over, all with unique forms and similar but distinct rules. India has the Varanas, a people of weremonkeys, and Tasherit the werelioness meets the group and agrees to travel with them. The pishtacos of Peru mention that werejaguars and werepumas used to exist, but were wiped out.

* FloatingContinent: Edo, also known as the Paper City, which floats above Tokyo thanks to an intricate system of immense balloons. It's also the only part of Japan that foreigners are allowed to visit, and how it stays still despite a lack of anchor is a zealously guarded secret.
* FurAgainstFang: In contrast to England and most of Europe, the Rakshasas and Varanas of India are bitter rivals and believe they have a divine mandate to fight. This caused a major diplomatic blunder when England reached out to the Rakshasas first, leading the Vanaras to refuse further diplomatic ties.

** The Spotted Custard trying to puff and making farting noises

** The werelions were once gods to the Egyptians, but this later turned to deep hatred and a desire to have all supernaturals eradicated. Now, they are reduced to a single group living on a false island in Lake Victoria.

* InsufferableGenius: Arguably Percy's defining character trait. He's the most educated person on the airship and often bemoans being surrounded by "lesser intellects", while showing off his own scientific mind at every opportunity.

* LastEpisodeNewCharacter: Arsenic Ruthven joins the group in ''Reticence'' and is co-protagonists with Percy.

* SpinOffspring: All four of the protagonists are direct or indirect offspring of the main characters in ''Parasol Protectorate''. Rue is the daughter of Alexia and Connell Maccon and adoptive child of Lord Akeldama, Primrose and Percival are the children of Ivy and Ormond Tunstell, and Quesnel Lefoux is the son of Angelique and adopted son of Madame Lefoux. ''Reticence'' also has Arsenic Ruthven, the daughter of [[BlackWidow Preshea]] [[MasterPoisoner Buss]] from ''Series/TheFinishingSchoolSeries''.

* AmbiguousDisorder: Percy is genuinely incapable of determining social cues, hates wearing specific types of clothes or having his routine disrupted, and hyperfixates on his work, traits of someone on the autism spectrum. [[spoiler:Rodrigo Tabarotti might be another example, as Percy immediately connects with him and the way he thinks in a way he hasn't felt with others before]].

* SpinOffspring: All four of the protagonists are direct or indirect offspring of the main characters in ''Parasol Protectorate''. Rue is the daughter of Alexia and Connell Maccon and adoptive child of Lord Akeldama, Primrose and Percival are the children of Ivy and Ormond Tunstell, and Quesnel Lefoux is the son of Angelique and adopted son of Madame Lefoux.

* UniquenessValue: Rue is the first and only known metanatural, a status that brings curiosity and contempt.