So I had an idea for an Undertale AU..
What if Chara fell into the underground, did everything they did down there, ate flowers, died, then realized it had all been a DREAM, and ran to Mt. Ebbot, and did it all in REAL LIFE. So it wasl ike, they told the future, in their dream, i guess.
Then Frisk would go through the whole thing as a dream, amd that would be really detailed, and a few things would probably be a bit different, maybe different outfits for characters and such. Anyways, then when Frisk completed the pacifist route, they would wake up, and it would end with them falling into Mt. Ebbot and hearing Flowey saying "Don't you have better things to do?"
...JUst an idea..anyone can use if they like..just credit me