THE TOOTH FAIRY COUNTRY IN HOGFATHER...

 ...is, for a good reason, similar to toddlers' crayon drawings/paintings. Because it has been created from the minds of toddlers. That is also why Death is powerless there, because toddlers cannot grasp the concept of death.

Hogfather, Terry Pratchett (TV Tropes)

Stock Object Colours: Discussed when Susan and the Oh God of Hangovers end up in the Tooth Fairy's country, which resembles a child's (toddler's) drawing. Susan realises what it is because (among other simplifications) the water in the creek is blue, the fish in the creek are bright orange, the treetrunks are plain brown, and the apples are bright red... even though creeks are usually transparent, freshwater fish are most often silver, treetrunks have a whole range of colors from brown to grey to green, and only some apples are red. But children (ie toddlers) draw brown treetrunks, orange fish, blue water, and red apples, green grass, and a buttercup-yellow sun, because that's what they "know" they're supposed to be. Terry Pratchett calls these Stock Object Colours the colours of the springtime of the eye. The phenomenon occurs because, according to Terry Pratchett, when you are a toddler or young child "everyone tells you grass is green and water is blue."

The Tooth Fairy Country has been created from the minds of young children (toddlers), and looks like a child's (toddler's) painting (think crayons). The sky is bright blue, the ground is bright green (grass sketched with bright green crayons, hills with slightly tremulous contours) the trunks of the trees are all plain brown, all those trees are lollipop-shaped with round blob-shaped tops and slender stick-shaped trunks, all apples on those trees are oversized and bright red, and the river is a block of deep blue liquid (when picking up some of the liquid, Susan realises the "water" is blue instead of transparent) through which orange cartoon fish swim. There are no bushes, neither any other fauna besides those stylized goldfish, and flowers similar to daisies, each one with two leaves, grow dotted across the bright green grass. The Sun is bright buttercup yellow with clearly visible rays. The clouds are all fluffy white cumulus. There are no variations in colour, or hues, or textures; everything is one colour. The sky does not extend as far as the horizon; in between the ground and the sky is an empty void, not occupied by black starry space or anything else. It is easy to see why the criminals hate it so much.

By a bend of the stream is the Tooth Fairy's tower, which on the outside looks like a stock one-family house with white walls and a red shingled roof, a single floor, four windows and a single front door, and gray smoke curling out the chimney like a curlicue or corkscrew. There is always a house like that in a crayon drawing or painting made by a toddler. (On the inside, however, the Tooth Fairy's tower looks way higher and bigger.)

The childlike quality of the Tooth Fairy Country is beginning to affect the criminals, and they begin to revert further into infantile mindsets (fear of Poorly-Lit Pareidolia for Chickenwire, fear of the dark and claustrophobia for Catseye, fear of bullying at boarding school for his feminine-looking curly hair for Sideney, Oedipus complex for the Lilywhite brothers).

It is impossible to die in the Tooth Fairy Country-a little child (toddler) believes that dead people have just "gone away". Therefore, when someone dies, they disappear back to the Discworld. People who die in the Tooth Fairy's castle or tower get teleported away. This is because the place is based on the imagination of children (toddlers), who do not really grasp the concept of death or what happens after you die.

Adaptation Distillation: The adaptation shows all the events as they happen chronologically, even those that Susan (and through her, the readers) does not learn about until almost the very end of the book (most notable are the relation between the Tooth Fairy's realm and children's ie toddlers' crayon drawings, how death is treated in the Tooth Fairy's realm, the outright spelling-out of Teatime's plan for the teeth starting with punching Banjo, and the no-longer-behind-the-scenes nature of Death's decision to impersonate the Hogfather).

The Discworld Wiki has no article for the Tooth Fairy Country but refers to it in the Hogfather article as "a world created by children's imagination." (No reference to Stock Object Colours or the colours of the springtime of the eye!)

Discworld Wiki: Anthropomorphic Personifications article 

The Tooth Fairy lives in an unreal place shaped by the idea of a child's painting. (No reference to Stock Object Colours or the colours of the springtime of the eye!)

Quoting the source material:

Susan slid off, trying to keep her gaze low. That meant she was looking at the vivid blue of the water. There were orange fish in it. They didn't look quite right, as if they'd been created by someone who really did think a fish was two curved lines and a dot and a triangular tail. They reminded her of the skeletal fish in Death's quiet pool. Fish that were... appropriate to their surroundings. And she could see them, even though the water was just a block of colour which part of her insisted ought to be opaque... 

She knelt down and dipped her hand in. It felt like water, but what poured through her fingers was liquid blue. And now she knew where she was. The last piece clicked into place and the knowledge bloomed inside her. She knew if she saw a house just how its windows would be placed, and just how the smoke would come out of the chimney. There would almost certainly be apples on the trees. And they would be red, because everyone knew that apples were red. And the sun was yellow. And the sky was blue. And the grass was green. 

But there was another world, called the real world by the people who believed in it, where the sky could be anything from off-white to sunset red to thunderstorm yellow. And the trees would be anything from bare branches, mere scribbles against the sky, to red flames before the frost. And the sun was white or yellow or orange. And water was brown and grey and green... 

The colours here were springtime colours, and not the springtime of the world. They were the colours of the springtime of the eye. 

'This is a child's painting,' she said.

The oh god slumped onto the green. 'Every time I look at the gap my eyes water,' he mumbled. 'I feel awful.'

'I said this is a child's painting,' said Susan. 'I've seen dozens of pictures of it,' said Susan, ignoring him. 'You put the sky overhead because the sky's above you and when you are a couple of feet high there's not a lot of sideways to the sky in any case. And everyone tells you grass is green and water is blue. This is the landscape you paint. Twyla (a little girl Susan tutors) paints like that. I painted like that. Grandfather (Death, for Susan) saved some of-' She stopped. 'All children do it, anyway,' she muttered. 'Come on, let's find the house.'

'What house?' the oh god moaned. 'And can you speak quieter, please?'

'There'll be a house,' said Susan, standing up. 'There's always a house. With four windows. And the smoke coming out of the chimney all curly like a spring. Look, this is a place like ... Death's country. It's not really geography.' 

The oh god walked over to the nearest tree and banged his head on it as if he hoped it was going to hurt. 'Feels like geo'fy,' he muttered. 

'But have you ever seen a tree like that? A big green blob on a brown stick? It looks like a lollipop!' said Susan, pulling him along. 

'Dunno. Firs' time I ever saw a tree. Arrgh. Somethin' dropped on m'head.' He blinked owlishly at the ground. '

's red.'

'It's an apple,' she said. She sighed. 'Everyone knows apples are red.' There were no bushes. But there were flowers, each with a couple of green leaves. They grew individually, dotted around the rolling green. And then they were out of the trees and there, by a bend in the river, was the house. It didn't look very big. There were four windows and a door. Corkscrew smoke curled out of the chimney. 

'You know, it's a funny thing,' said Susan, staring at it. 'Twyla draws houses like that. And she practically lives in a mansion. I drew houses like that. And I was born in a palace. Why?'

'P'raps it's all this house,' muttered the oh god miserably.

'What? You really think so? Kids' paintings are all of this place? It's in our heads?'

'Don't ask me, I was just making conversation,' said the oh god. 

Susan hesitated. The words What Now? loomed. Should she just go and knock? And she realized that was normal thinking... 

From Zahnturm in the German thediscworld wiki:

Die Welt, in der der Zahnturm steht, sieht wie ein Kindergemälde aus. Die Landschaft besteht aus mit Buntstiften gestricheltem Gras, die Hügel und Berge haben leicht zittrige Umrisse und am Himmel ziehen kringelige Wolken und eine knallgelbe Sonne mit deutlich sichtbarem Strahlenkranz. Im kleinen Bach aus tiefblauem Wasser springen die Fische und an den Bäumen hängen überdimensionale rote Äpfel.

Tor.com

Terry Pratchett Book Club: Hogfather, Part III

Emmet Asher-Perrin

Fri Aug 5, 2022 11:00am

Meanwhile, back at the main plot, Binky takes Susan and the Oh God to Violet’s location which turns out to be a children’s painting complete with a children’s drawing of a house.

Susan and Bilious arrive at the land where Violet is being held, and she finally realizes where this place is: It’s a child’s painting. She wonders why all children seem to draw things exactly like this, and Bilious (whose potion has worn off so that he’s feeling incredibly hungover again) suggests that perhaps children are all painting this place specifically.

Susan goes into the children’s drawing house with Bilious and finds a large mound of teeth on the floor, with a chalk circle indicating where it’s meant to go.

• There’s a fairly large aside to be made here about the psychology of children’s drawings because they really are a fascinating subject that still confuses psychologists, as far as I understand it. It’s being used here as a kind of chicken-or-egg scenario because do children really draw this place, or is it children’s innate understanding of this place that makes it real? But honestly, all I want to do is talk about perspective and how kids decide to make certain objects/subjects gigantic and others not. That would have changed that nature of this place a great deal.