Jenny Green-Teeth is the first wave of the Queen of Fairyland's attack against Tiffany Aching. She makes her appearance in the first Tiffany Aching book, The Wee Free Men. She has long skinny arms that emerged from the water and clawed at the place where Tiffany had been, a thin face with long sharp teeth, huge round eyes, and dripping green hair like waterweed. Tiffany knows her from a picture in one of the few books in the house, The Goode Childe's Booke of Faerie Tales.
Being of an enquiring mind, she wants to know what the book means by "eyes the size of soup plates", and measures some from the dresser. Eight inches, actually. Being the kind of person who runs towards things rather than away from them, she takes the largest cast iron frying pan from the kitchen, and using her small brother as bait with the promise of 'sweeties', lures the creature out of the stream again, whereupon she gives it a crack across the head with the frying pan. Jenny may have been at a disadvantage, possibly bewildered at being in a stream when her natural habitat is stagnant water, but the fact that the frying pan was made of iron was decisive.
Tiffany's wish to know more about Jenny Green-Teeth leads her to Miss Tick. Jenny Green-Teeth is woven from her own imagination as much as anything else, but Miss Tick explains that all the monsters are coming back, even the ones out of books, the start of a major incursion with nothing standing in the way apart from Tiffany.
Miss Tick describes Jenny Green-Teeth as "only a Grade One Prohibitory Monster". This refers to a schema which appears to be of Miss Tick's devising and which she may have set out in a book called the Bestiary of Transient Monsters. The schema is summarised on a sample diary page provided in The Illustrated Wee Free Men.
- Grade 1: monsters invented by adults to scare children from dangerous of forbidden places (prohibitory) - Jenny is a good example of this, designed to keep children away from dangerous water where they could drown.
- Grade 2: monsters invented by adults to scare anyone, anywhere. One of the examples is The Headless Horseman.
- Grade 3: monsters by accident (mostly). e.g. The Eater of Socks.
- Grade 4: monsters here for purposes of their own (such as the Hiver).
"Jenny Green-Teeth" is a figure in English folklore coming from Lancashire folk tales about a spirit or boggart who lived underwater. Her presence is indicated by the growth of duckweed, which thrives in still fresh water. A river hag, similar to Peg Powler or a grindylow, she is often described as green-skinned, with long hair, and sharp teeth. The name is also used to describe pondweed or duckweed, which can form a continuous mat over the surface of a small body of still water, making it misleading and potentially treacherous, especially to unwary children. In folklore she pulls children or the elderly into the water and drowns them. Like many legends of the fairy world, her existence is used to explain natural occurrences. In this case, Jenny Green-Teeth specializes in drowning people, so any accidental drowning of a child can't be the result of an inattentive family member but has been caused by malevolent fairy people. She is called Jinny Greenteeth in Lancashire, but in Cheshire and Shropshire she is called Ginny Greenteeth, Jeannie Greenteeth or Wicked Jenny.