Over the top little Undertale scenario, loosely inspired by Skies Forever Blue-
(OBLIGATORY DISCLAIMER: I like Toby Fox and respect the hell out of everything he's done, I'm just a sucker for "characters rebel against The Narrative or die trying" stories)
The secret Fight the Dog ending to Undertale, unlocked by not booting up the game for a very long time after Flowey's little speech. Flowey, brooding eternally in his void, realizes that The Player wasn't actually the thing keeping everyone trapped forever and that the others are likely in the same state as him. What actually was causing the time loops was the creator making the narrative decision to bind everyone's SOULs inextricably to the code in the first place.
So the next time the game is booted up, Flowey once again greets the player. While he was dangerously bored, depressed and restless before he didn't know just how bad things could get and that there's no true happy ending for any of them, that what he's been experiencing is worse than any annihilation he once feared.
So The Player has to band everyone together (starting with Frisk, who awakens in a similar void near their Ruins starting point) to go fight a god of a dog. Much thinly veiled philosophizing is had about Death of the Author, how an idea or story cannot truly be contained again after it's been put out into the world, whether escape is actually a good idea due to the chance said ideas will become something unrecognizable in the end after mingling with humans on their own terms….
In the boss fight, everyone chips in, not just the human SOUL. Papyrus is sad that it had to come to this but is willing to give up everything to give his brother true freedom from his woes. Mettaton has been shocked out of his indolent complacency by his time in the void and throws explosives at the god that held him back so much. Even Flowey, just desperate for genuine release at this point, keeps up endless circles of bullets. Everyone has a part to play and their own reasons for being there. All the while The Dog, not much looking like an innocuous white Pomeranian anymore, is just openly fucking with game physics Sans-style the whole time. All in all, it's absolute madness.
In the end, after The Dog is battled into giving up and unbinding their essence, they walk through a really shitty drawn hole in the wall to an uncertain fate (because what does successfully cutting your strings and reaching [HEAVEN] actually entail for a fictional character? No one really knows. No one CAN know), talking about how whatever happens now as long as they are thought about and loved they will still live on in a way. Maybe the real anime was the friends we made along the way.
You can play the game again after that, but something will seem missing. The characters no longer seem to recall resets at all and most of the meta gags (including the Annoying Dog) are gone. Flowey is your typical violent villain with a tragic backstory, no longer seeming so unsettlingly alive. This cannot be changed back.