"Every established kitchen has one ancient knife, its handle worn thin, its blade curved like a banana, and so inexplicably sharp that reaching into the drawer at night is like bobbing for apples in a piranha tank."
All Crimes Are Equal: In Lilith's Genua, thieves are beheaded on the first offence (under the logic that while cutting their hands off keeps them from stealing again, cutting their heads off keeps them from thinking of stealing again.)
All Girls Want Bad Boys: The descriptions of Greebo's human form indicate that a certain amount of badness becomes utterly irresistible.
Given where female gazes tend to wander, it's a large amount.
Assurance Backfire: When Magrat is feeling deeply embarrassed and uncomfortable about having to pose as Emberella at the ball, and the other witches try to help...
"Don't worry," said Granny, "We'll be there too."
"And that's supposed to make me feel better, is it?"
Baleful Polymorph: Lily turning the footmen, who we spent a while getting to know and sympathize with, into beetles. And stepping on them.
Bested At Bowling: Granny wins back all their money (and more) from some card shark riverboat gamblers via the astute application of 'headology'. She also uses a little magic - not so that she wins, but to prevent her opponents from cheating (smashing a mirror, making an ace fall out of a man's sleeve).
Bewitched Amphibians: Inevitably discussed, as a fairy tale classic. And inverted — the Duc is a bewitched amphibian, but he's not a man who was transformed into a frog...
The Big Bad Wolf: The main villain warps reality so it'd be like fairy tales. This includes making a wolf think more like a human so it will be a better villain (talking, opening doors, showing human-like cunning and so on). The wolf suffers horribly, stuck between species, and begs for a Mercy Kill.
Blessed with Suck: Old Mother Dismass has Second Sight, which means she can see clearly into the future and the past. Just not in the present, and randomly has conversations a few months in advance. This makes her something of a near-Bursar levels of Cloud Cuckoolander at times.
Breaking And Bloodsucking: Subverted, a vampire abjectly fails to get into the rooms at the inn where the three witches are staying. Magrat fails to get the point, declares the room too stuffy, and opens the heavy shutters - concussing the vampire on the other side who is trying to get in.
Brick Joke: Nanny remarks about foreign turns of phrase, saying that "bum" means "hobo" in some regions. Later, Granny dons a stolen dress with a bustle, and refers to it as an extra bu... hobo.
Cannot Tell a Joke: Granny completely and repeatedly failing to tell the alligator sandwich joke, with such punchlines as "And don't take too long about it".
Chekhov's Gun: Early in the book Magrat explains a bit about the judo-like martial arts she's studying; namely that it's based around using your enemy's power against them. While the other witches don't seem impressed by it at the time, during the climax, Granny defeats Mrs Gogol, who is threatening her with a Voodoo Doll, by thrusting her hand into a blazing torch up to the elbow, causing the doll to burst into flames while her arm is unscathed. Even for Granny, this is a Crowning Moment of Awesome. She even glances at Magrat before doing so as a subtle acknowledgement.
Continuity Nod: This isn't the first time Death has received a compliment on the quality of his "mask". In The Light Fantastic his was at a (different) party when he is summoned by the wizards, and comments that it's going to go downhill at midnight, because:
Death: That's when they think I'll be taking my mask off.
Evil Is Hammy: Subverted, to Granny's immense rage. Lily spent her whole life convinced that she was the good sister who was putting the needs of others over her own, and, so convinced of her own martyrdom, thus made herself a very understated and sinister foe. To Granny, who knew for a fact who was the good sister and who was the bad, this is almost a greater sin than any of Lily's actual wrongdoing, because Granny would have at least enjoyed it, making whole banquets of her surroundings and being bad enough to even top the legendary Black Aliss, who (when in Lily's role) could keep multiple stories going at once in the same place.
Fantasy Counterpart Culture: Genua is New Orleans + Disneyworld with a slight dusting of 18th century Revolutionary France, but en route they also pass through areas based on Spain (the Running of the Bulls, or the Thing With the Bulls here) and the Hammer Horror version of Transylvania - what would later be named as ▄berwald. According to Terry Pratchett:
"... Genua is a 'sort of' New Orleans with a 'sort of' Magic Kingdom grafted on top of it. It had its genesis some years ago when I drove from Orlando to New Orleans and formed some opinions about both places: in one, you go there and Fun is manufactured and presented to you, in the other you just eat and drink a lot and fun happens."
Fantasy Kitchen Sink: The Discworld itself is already one, but under Lilith, Genua is a Fairytale Kitchen Sink.
Foolish Sibling, Responsible Sibling: Granny Weatherwax wanted to be the irresponsible evil one, but because her elder sister, Lilly, beat her to the punch on that she felt forced to be the responsible good one. When both sisters are witches, you can see how this complicates family relationships.
Forging The Will: Lampshaded. When being told the story of how the old Baron of Genua died, Granny Weatherwax and Nanny Ogg both make the Genre Savvy assumption that the one now in control, the Duc, has control because of a will discovered shortly after the Baron's death with the ink still wet.
Fun with Foreign Languages: The travel segments, which consist of Nanny speaking in "Foreign" (e.g. "Garkon? Mucho vino aveck zei, grassy ass.") Her translation of Cassanunda's serenade inverts this.
Going to See the Elephant: Mentioned by name as the last line in the book: "Foreign" is a odd place where they do things wrong, speak funny lingo and eat strange food, so our heroes can't wait to get back home. Still, in the end, they take the time to enjoy the sights: "But they went the long way round, and saw the elephant."
The Good Guys Always Win: Invoked. Lily is confident of her victory because she knows good always triumphs over wickedness; unfortunately for her, she's wrong about which part she plays.
Happiness Is Mandatory: Lillith turns Genua into a sparkling clean city full of blankly smiling citizens by dint of torture and execution.
Happy Ending: Heavily subverted, with Lily murdering and ruining people's lives to get to what the stories demand. Then played straight, releasing the city from her grip lets everyone relax and party.
Hollywood Voodoo: Semi-averted; the version here is well-researched but, like most Discworld things, a hodgepodge and mixture of real world examples.
Humanity Ensues: Greebo, and the mice which are transformed into footmen. Also Emberella's "evil stepsisters," which Lilith made from snakes, and an unfortunate wolf which was sort of turned into a human...
Human Resources: Stories use people to perpetuate themselves. Anybody who fits a certain set of characteristics may find themselves absorbed into a story and forced to act in whatever role is given to them, even if it ends with them being devoured by a wolf or marrying a frog.
Instant Waking Skills: Thanks to her strong sense of self, Granny Weatherwax can skip all the little questions most people have to ask themselves on waking up (like "Who am I?" and "Where am I?") and get right to the actual getting out of bed.
Light Is Not Good: Lily dresses all in white and thinks of herself as a creator of happy endings.
Locked Out of the Loop: Ella isn't told that she's the Baron's and Mrs. Gogol's daughter, first because Lily wants her to be pliable, and later because Mrs. Gogol agrees not to interfere with her life.
Lunacy: This book introduces the Discworld concept that the most magical phase of the moon is not the full moon, nor a mystical crescent, but a half moon — the Balance Between Good and Evil.
Magic Mirror: It's specified that using one mirror for magic is fine, but Lily stands between two of them...
Magic Poker Equation: Invoked by Granny Weatherwax to win back the witches' travelling money (and Nanny Ogg's broomsticks) from some card sharps.
Meaningful Name: Baron Saturday, obviously, but Mrs Gogol and her familiar, Legba, both of whom are named after Loa as well.
Mercy Kill: The Big Bad Wolf willingly goes to the woodcutter's axe because Lily forced it to think human thoughts with a wolf mind, a terrible thing to do to a simple predator. (This revelation to the witches is also something of a Moral Event Horizon for Lilith.)
Nineties Anti-Hero: Greebo as a human is described as, among other things, "a pirate who just raided a ship carrying leather garments for the discriminating."
Nonsense Classification: The dwarf classification of rocks starts out well, but goes a bit weird near the end: "igneous rock, sedimentary rock, metamorphic rock, rock underfoot, rock dropping on your helmet from above, and rock which looked interesting and which they could have sworn they left here yesterday".
Palantir Ploy: Lilith can use her magic mirrors to scry through any reflective surface in the world. Subverted, as her inability to find what she wants to look at through any method other than manually scrolling through all available reflective surfaces makes it a bit Awesome but Impractical.
Prince Charming: Subverted with the Duc, despite Lily trying to make him seem that way.
Public Execution: Some countries cut off a thief's hand so he won't steal again. Lady Lilith cuts off his head so he won't think about stealing again. This is also a good example of the reaction of the public showing the nature of the society; after years of Lilith's rule, the public don't react at all, they just have a dead-eyed stare.
Reality Ensues: Whenever a story comes to an end or is somehow subverted, everything then proceeds as it normally would.
Secret Test of Character: At the end of the book, Granny and Lilith become trapped (separately) in a limbo full of mirrors after the magical explosion that "kills" them. Death is there, and he tells Lilith that to get back to the land of the living, she needs to find her real self amongst the mirrors, and Lilith starts desperately looking. When Granny's turn comes and Death tells her the same challenge... Granny points out that she's standing right there. Guess who leaves the limbo.
Shout-Out: The early part of the witches' journey is a parody of The Lord of the Rings and derivative works, with the 'invisible dwarf runes' on the door in the mountains ("I can't see 'em" "That's how you know you've got your money's worth, with invisible runes") and, most notably, the boat passage on the underground river - at one point a slimy creature on a raft appears and says "'Ullo... it'sss my birthday..."
The "invisible runes" part even includes "She struck the door and spake thusly: "Open up, you little sods!"
Mrs. Gogol's hut can move about on duck feet, as a wetlands-adapted variant of Baba Yaga's chicken-legged hut in Russian folklore.
Nanny Ogg gets a house dropped on her head by a tornado, then dwarfs wander up and ask for her shoes, all while on a yellow brick road, a la The Wizard of Oz. Notably, Nanny Ogg is wearing red shoes, although they are not magical; their main quality is the ability to have a cart run over them and the feet inside to remain unscathed. Cover art also shows she has stripy stockings like the witch in the movie.
Nanny kicked her red boots together idly.
"Well, I suppose there's no place like home," she said.
Standing outside the Duc's chamber, Nanny recollects a story similar to The Bluebeard legend.
Stealth Pun: There's a couple of puns where the first two witches give an outright pun or Shout-Out but Nanny Ogg delivers the stealth pun.
When stuck in a The Wizard of Oz parody, the witches are calling out each other's behaviour.
"What some people need", said Magrat, [...], 'is a bit more heart."
"What some people need", said Granny Weatherwax, [...], "is a lot more brain."
What I need, thought Nanny Ogg fervently, is a drink. Dutch Courage - just what the Wizard gave the Lion in the book.
The three of them are deliberating on the idea of a transport system built on broomsticks. Their ideas for names are puns on well know real world airlines but Nanny Ogg gets cut off before she finishes hers: "Vir-". However, note she is looking from Granny to Magrat and being rather coquettish. Consider Magrat's role in The Hecate Sisters trio. Virgin.
"Samedi Nuit Mort": Samedi = Saturday; Nuit = Night; Mort = Dead. Think Terry got a chuckle from Saturday Night Live?
Sunglasses at Night: The Duc, because on the Discworld one's true nature always shows through one's eyes, and he has the eyes of a frog.
Translation By Volume: This trope is Granny Weatherwax's default form of communication when dealing with foreigners during the witches' travels.
Trampled Underfoot: Deliberately invoked on some coachmen by Lily, who turns them into beetles and stomps on them for failing her. Also the fate of the Duc, when he reverts to frog form and fatally encounters Baron Saturday's descending foot.
In a more meta interpretation of the trope, part of the book's theme is the idea that fairytale stories repeat themselves, wear a groove in the world and then subvert reality so that, for example, "it is now actually impossible for the third and youngest son of a king to set out on a quest that has claimed his two older brothers, and not succeed." Lily's power comes from manipulating the stories to her own ends.
Even when, as in the case of the stories she's using for her main plot, she's actually got at least one of them backwards.
Woman in White: Lily, trying to invoke a trope. (And Granny, briefly, but she isn't happy about it.) Incidentally, this is perfectly indicative of Granny's speech, which fittingly blurs the line between a Hannibal Lecture and a Shut Up, Hannibal!. Granny considers Lilith's greatest wrong against her to be saddling her with the role of good sister while she (Lilith) squanders her role as the evil one.
Wrong Genre Savvy: Lilith is this—she thinks she's the kind fairy godmother who's giving everyone a happy ending, to the point where she invokes happy fairytale endings at sword-point. You'll live happily ever after or else.