The universe (which others call the Library) is composed of an indefinite and perhaps infinite number of hexagonal galleries, with vast air shafts between, surrounded by very low railings.
-Library of Babel, Jorge Luis Borges
When famas go on a trip, when they pass the night in a city, their procedure is the following: one fama goes to the hotel and prudently checks the prices, the quality of the sheets, and the color of the carpets. The second repairs to the commissariat of police and there fills out a record of the real and transferable property of all three of them, as well as an inventory of the contents of their valises. The third fama goes to the hospital and copies the lists of the doctors on emergency and their specialties.
After attending to these affairs diligently, the travelers join each other in the central plaza of the city, exchange observations, and go to a café to take an apéritif. But before they drink, they join hands and do a dance in a circle. This dance is known as “The Gayety of the Famas.”
When cronopios go on a trip, they find that all the hotels are filled up, the trains have already left, it is raining buckets and taxis don’t want to pick them up, either that or they charge them exorbitant prices. The cronopios are not disheartened because they believe firmly that these things happen to everyone...
-Cronopios Y Famas, Julio Cortazar, tr. Paul Blackburn
The Merchant is a blue skinned man sitting on a blue-green rug next to some cards, a small chest, a bag, and a knife. He is wearing a mask covering his face and a blue cloak. He acts friendly towards the player and talks to them while they view and purchase his wares.
-Slay the Spire Wiki
There is a specific genre--or maybe just category--of fantasy I'm going to call "Bottle Fantasy". The simplest way to describe Bottle Fantasy is literally no-one has a normal life.
Let me be precise, though:
While most imaginative fiction (from the Godfather to Lord of the Rings) simply tells a story which focuses on something more exciting than human life as we know it, Bottle Fantasy takes place in a whole universe with no clear place recognizable human life as we know it. In a Bottle Fantasy, nobody gets born, then lives a whole life that looks (at least from the outside, regardless of the physical laws involved) like one that would happen in the real world, and then dies in a real-world way.
This isn't the same as just an imaginary world or universe--Middle Earth, it is strongly implied, either is the past of our world or one a lot like it, which means it both has people living normal lives in it and that it might one day mellow out and look like our world. Star Trek makes a place for our lives: in the past, Star Wars posits itself in the past--and far away. Moreover, all these fictional worlds at least want us to believe they have basically recognizable economies, human biologies (decapitation kills humans), etc.
Aside from the absence of Christianity, vanilla D&D could plausibly take place in the world that a very superstitious peasant suspects is just outside his door.
To simplify, hopefully: in most fantasy, there are dragons but the average peasant hasn't seen one. In Bottle Fantasy, there aren't average peasants and there never have been. All people eat starlight instead of meat, or there may be no people, only spheres, or all people are just stacks of owls in costumes.
Bottle Fantasy is in a bottle--while things may be analogous to our world, there is no in-world connection to our normal world.
Pac-Man, as presented in the original video game, is technically a Bottle Fantasy: there are no people, only Pac-Man, ghosts, dots and fruit. In Borges' Library of Babel there is literally no world except the library full of hexagons.
The world Julio Cortaza describes above in Cronopios Y Famas might be a Bottle Fantasy--there are doctors and taxis, but it's suggested that all people in the world of the book are Cronopios, Famas or Esperanzas--creatures who all act in a stylized way. It is unclear whether the doctors and taxi drivers are people who act in a normal way other than giving trips to Cronopios et al.
Like most genre categories, there's a spectrum. With "Total Bottle Fantasy" (world unconnected to our own operating on rules all its own) to "Almost Bottle Fantasy", some examples:
- Planescape is the closest official D&D comes to Bottle Fantasy. Though you can travel and get to a world where regular people exist doing regular things, it's assumed you'd spend almost no time there and that the vast majority of the action takes place in worlds with alternate life patterns, economies and day-to-day physical laws.
- Lewis Carroll's Alice books would be Bottle Fantasies if it wasn't for the fact that Alice is an ordinary girl from our world.
- Likewise, it's spawn Red & Pleasant Land would be Bottle Fantasy if it weren't for the fact you can get there from a more recognizable world.
- Mario's gameworld would be Bottle Fantasy if it wasn't for the fact that the early games posit that Mario and Luigi were regular plumbers from our world who just went into the pipes to clean out crabs and turtles.
- Eberron is right on the edge, because it's implied everything that you can do in normal D&D is somewhere in Eberron, that means that there are people who just, like, go to taverns and work as regular blacksmiths, etc. There's probably versions of Eberron where even the farmwork and daily drudgery is obviously magic-based, but I don't think anyone's ever gone into that much detail.
- Slay The Spire is a Bottle Fantasy: there is no clear evidence of normal life anywhere. The clearest examples of real lives we see are communities trying to live within The Spire who definitely survive on weird unreal processes.
- Candyland is an example of a minimalist Bottle Fantasy. There is naught but travelers and candy.
- A lot of OSR gameworlds posit or begin to posit Bottle Fantasies.
- Superhero worlds aren't generally Bottle Fantasies, since normalcy exists as a thing from which superheroes and villains emerge.
- Sci-fis usually aren't Bottle Fantasies because they posit a normally-functioning historical Earth either far away, in the past, or existing just before the introduction of some sci-fi idea.
Some general characteristics of Bottle Fantasies in different media:
- Bottle Fantasies are more common in video games and board games than most other media because the effort to create this kind of game starts with the fun/action/adventure part of the world--the part you, as a main character, play with--and programming in the normal world or references to it is often just more work than making something up. As a game creator with these games you start with what's unusual and then work your way out. You start with jumping on turtles and only tell us what a normal day as a plumber is like if you have extra time.
- Bottle Fantasies are less common in tabletop RPGs (especially popular ones) because, conversely, the players' tactical choices and the game master's adventure-building choices rely heavily on assuming there's a world outside the game text that functions in a familiar way. For example: few RPG texts bother to explain that rivers are full of water and flow in one direction or that wood floats--but most RPG creators assume that these two facts can be assumed by players who want to build a river-raft to get somewhere. Everytime you want to remove a real-world assumption you need to type at least one sentence ("there are no rivers in the world of Dark Sun") and every time you want to change it, you need to type even more ("instead there are seas of silt"), and then you have to explain the implications, because it's an RPG and the world has to function even when the author isn't narrating it ("Most people get their water from...")
- Bottle Fantasies in live-action film are even rarer than in tabletop RPGs because in these films (1) You have to take the raw material of reality and transform it to get a fictional world (2) This is expensive (3) Expensive films often have to pay for themselves by being popular (4) A wholly Bottled world, though offering opportunities for exciting special effects, is less likely to be relatable, which limits its popularity. The compromise live-action film generally makes is to offer a Mario or Alice-style "visitation" narrative like Tron where someone from our world goes to a mostly Bottled world. It is a feat of rare daring for a filmmaker to make a complete Bottle World, especially for adults.
- Conversely, Primitive Bottle Fantasies in animation are common--especially in experimental or student animation because, say, "Dots vs Lines" is very doable.
- Bottle Fantasies in written fiction are common in short stories, but rare as novels. While many fantasy, sci-fi, and straight literary writers have produced Bottle Fantasies as short thought-experiments, its hard to think of a novel's worth of conflict over things that don't exist in our world, and you have to be pretty good, or at least pretty driven, to do it.
In sculpture, they talk about additive and subtractive sculpture--in additive sculpture you pile up material (say: clay, or legos) until it looks like the thing, in subtractive sculpture you carve away (stone, or the like). In fiction, we can talk about reality like a material: there are media where you start with a real thing, like actors on a stage, and alter them to seem like characters in your story, and there are media where you start with nothing--an empty canvas or page--and add things.
The pattern here is: if working a medium starts with reality and then alters it in order to produce its basic material, then Bottle Fantasy is unusual, if working in a medium starts with nothing and getting something to resemble reality is itself a complex act of craft, Bottle Fantasy is more common, since a fantastic world is often easier to produce than a real one. Bottle Fantasy is easy in painting (look: a world consisting of a circle and nothing else) and hard in theater (every actor needs to be disguised as not-an-actor, the stage might have to be rigged with wires and mirrors to present alternate physics).
Oddly, this puts tabletop RPGs on the "start with reality, then alter it" side of the equation.
Bottle Fantasy in RPG or live-action film are, thus, very ambitious projects. Building a world that functions for hours without any parts that default to the real world (or at least some shared conception of it) is a bit like trying to build a car that works without gas or electricity or even steam.
Bottle Fantasies are, almost axiomatically, imaginative but inaccessible. And the more imaginative they are, the less accessible they become.
Probably the ur-example in tabletop is Empire of the Petal Throne / Tekumel --while there are farmers in Tekumel, they're from no extant culture (when it is earthlike, Tekumel itself mixes South Asian and Mesoamerican influence, so you can't rely on one or the other the way you can assume anything left undescribed in Middle Earth is just "as you guess England circa 1200 would be") and the layers of ritual and invented religion intentionally insert themselves between players and their assumptions. Even Tekumel has a "visitation" narrative built in--players in the original game are supposed to be untutred foreigners. It might not be technically Bottle Fantasy as I've defined it, but it's close and presents the problems and opportunities of the genre.
Bottle Fantasy in RPGs is kind of great, in that it appeals to the game-masterish desire to invent everything from the ground up--"All arrows are petrified snakes here because there's no wood!" and it's kind of horrible in that it forces you to invent everything from the ground up--"Uh, if there's no wood, is there wine? What's it aged in? Wait, if there's no wood, are there vines?" etc.