ChatGTP made an UNDERTALE AU, here’s how it did:
Sure! Here’s a fresh Undertale AU concept you can build on:
AU Name: FractureTale
A timeline shattered… and a world trying to stitch itself back together.
Core Concept
After a massive anomaly, the Undertale timeline BREAKS into overlapping fragments. Characters now experience multiple versions of their own histories at once—memories, personalities, and relationships blend or conflict depending on which “fracture layer” influences them at the moment.
Instead of RESETs, the world now experiences FRACTURES—sudden shifts where the environment or characters momentarily reflect a different version of the past.
World Changes
Fracture Zones
Areas of the Underground randomly slip into alternate states.
Examples:
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Snowdin Loop: Sometimes empty, sometimes crowded—residents flicker in and out.
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Hotland Overheat: Machinery alternates between meltdown mode and complete shutdown.
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Ruins Echo: Dialog from past timelines repeats, distorting into warnings.
Character Variants
Sans — “Patch Sans”
A version of Sans who remembers every timeline at once.
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Wears a half-normal, half-glitched jacket.
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Speaks in mixed fonts when the fracture overtakes him.
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Humor darker, but still kind at core.
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Trying to “sew” the timeline back together using a mysterious device called The Stitcher.
Papyrus — “Optimist Papyrus”
His personality stays stable across timelines—his optimism acts like a natural anchor.
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Because of this, fractured characters gravitate toward him for stability.
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Builds “Hope Beacons” around the Underground to stabilize Fractures.
Frisk — “The Carrier”
Frisk is uniquely tethered to all timeline layers.
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Sometimes temporarily becomes an alternate version of themselves (pacifist, neutral, genocidal), depending on fracture pressure.
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Their choices determine which fracture eventually becomes the true timeline.
Flowey — “Rootless Flowey”
Has lost connection to Chara and can’t fully stabilize in reality.
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Appears as flickering versions of himself—happy, cruel, passive, terrified.
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Wants to use the fracture to recreate the exact timeline he prefers.
Themes
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Identity when your past is unstable
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Memory versus reality
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Can you fix something that never had one “correct” form?
Plot Hook
A catastrophic fracture is forming at the Barrier—if it fully breaks, all timeline fragments will collide into a paradox that erases the Underground entirely.
Frisk must choose which version of the world deserves to survive.
Sans refuses to let the kid make that choice alone.
Flowey thinks he should be the one to choose.
The final choice determines which fracture becomes canon.
If you'd like, I can expand on:
character designs
powers/attacks
story arcs
music themes
a full route system (Pacifist/Neutral/Fracture/Collapse routes)
Just tell me!
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