Undertale AU Wiki
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Created by Lerua

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Undertale Alternate Universe (AUs) are what-if changes to the universe of Undertale.

AU categories are used to differentiate AUs and to avoid confusion between AUs (categories are not AUs themselves).

An AU can fit under multiple categories.

AU Types

The basic types of AUs.

Switch Up

Some or all of the canon Undertale characters swap roles and/or personalities with or shift into the roles of the other canon Undertale characters. e.g: Sans replaces Toriel.

If there is an in-universe reason for characters to change roles from their original ones, it doesn't fit in this type either. In that case, the AU is most likely in the Continuity Change and Special Event types.

Crossovers

AUs where the characters of Undertale are replaced by those of a different franchise, such as a show or game. If the characters and/or setting of Undertale are placed in a different franchise, Continuity Change - Crossworld should be used instead.

This is NOT meant for crossover stories between AUs.

Basic Change

Main article: Basic Change

Basic Change AUs are AUs that have some fundamental aspect from Undertale or, in the case of AUs of AUs, the base-AU changed in such a way that everything is affected. Whether that be where all the Monsters are instead gods (like Reapertale), where all the Monsters are violent, fell creatures (like Underfell), or where the entire world has been altered from the world of Undertale or the base-AU (like Dreamtale), they are all Basic Change AUs. AUs where all the characters are the same, or the same character from multiple universes take up most of the cast are also Basic Changes.

Story Overhaul

Story Overhaul AUs are AUs that completely change the foundation of the story of Undertale or, in the case of AUs of AUs, the base-AU in such a way that it still clearly resembles its inspiration, while its premise is disconnected from it (like Reapertale).

Theme Overhaul

Theme Overhaul AUs are AUs that completely overhaul the general theme or "feel" of Undertale or, in the case of AUs of AUs, the base-AU. This can either be simply aesthetically, such as Outertale, or alter the characters' personalities, such as Underfell. The base plot is kept mostly unaltered.

World Overhaul

World Overhaul AUs are AUs where the world of Undertale or, in the case of AUs of AUs, the base-AU is completely overhauled to the point that there is barely any resemblence to the world of Undertale or the base-AU.

AU Where Everyone is the Same Person

An AU where everyone is the same person is, as the name suggests, an AU where a large number of characters are the same character. This doesn't just include AUs where all characters are, for example, Undyne (like Undynetale), but also AUs where a bunch of the same character from many different universes are present for the story, and take up a majority of the cast (like Christmas Party).

Continuity Change

Main article: Continuity Change

Continuity Change AUs, or Concept Change AUs, are AUs that modify the continuity of Undertale or, in the case of AUs of AUs, the base-AU in some fashion. Whether the AU takes place before the main story of Undertale, during the same time-period, or after—so long as the AU doesn't qualify for any other AU Type—they're all Continuity Change AUs. AUs that place the world of Undertale into the continuity of another IP (such as EarthBound) are also Continuity Changes.

Backstory

Backstory AUs are AUs that take place before the events of Undertale or, in the case of AUs of AUs, before the story of the base-AU, but don't change anything that would happen in Undertale/the base-AU.

The timeframe of a Backstory AU can proceed to take place during Undertale's events, as long as it does not conflict with anything that happens in-game.

Special Event

Special Event AUs are AUs that change the plot of Undertale or, in the case of AUs of AUs, the base-AU in some fashion, generally through a special event that occurs that otherwise wouldn't happen. Whether this sudden change happens before the main character (Frisk in Undertale) enters the Underground or while the main character is in the Underground, both are Special Events.

Sequel

Sequel AUs are AUs that take place after the main story of Undertale or, in the case of AUs of AUs, after the story of the base-AU.

Crossworld

Crossworld AUs are AUs that place the world of Undertale or, in the case of AUs of AUs, the base-AU (whether it be the characters or the entire setting) into the world of another Intellectual Property (such as EarthBound or Pokémon), or place characters from another Intellectual Property into the world of Undertale.

Self-insert

AUs in which the characters are replaced with real people.

AU Tones

The tone of AUs.

Serious

AUs that, as opposed to Comedic AUs, actually hold a serious story and such. Just because an AU has a serious tone does not mean that it must be serious all the time, just most of the time.

Semi-Serious

AUs that have a balanced mixture of Serious and Comedic elements.

Comedic

AUs that are mostly comedic in nature. Bear in mind that a Parody can be either dark or comedic so Parodies and Comedic AUs aren't necessarily the same thing. Nevertheless, they can also be both.

Fell

AUs that feature horrible, evil, and/or murderous Monsters.

Monstrous

Warning: Some of these AUs contain themes that may be disturbing to some viewers. It is suggested you read the short bios of these before reading the actual AU!

AUs that have a balanced mixture of Fell and Horror elements.

Horror

Warning: Some of these AUs contain themes that may be disturbing to some viewers.

AUs with the goal of creating something scary, insane, or disturbing. Some AUs that follow the genocide route are also found here, but not all are geno-route-only. Some possible themes include suicide, drug use, alcohol use, depression, death, gore, insanity, disfigurement, pain, etc. Horror can also include Terror, and effects on psychology. This could include things like dystopias and the like.

It is suggested you read the short bios of these before reading the actual AU!

Medium

The way the AU's story is told.

Animation

Stories told through an animation.

Comic

Stories told through comics.

Games

Stories told through a game.

Written story

Stories told through a book.


Miscellaneous AU Categories

Categories that don't fit in the above categories.

Community Shared

AUs that are generally seen as being "open for use" without the need to request permission from a given AU author, creator, or owner.

AUs of AUs

AUs that are modifications to or branches of pre-existing AUs. This is not to be confused with takes on AUs.

Outside the Underground

The story does not, within its entire story, take place within the Underground, but does take place within a Universe. Only applies to AUs that occur during the resetable timeline.

All items (484)

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