So, I had an idea a while back. I'm not very clever in level designing nor do I have the attention span to make an entire level, so I guess I'll share my idea with the community.

So, the general idea is the player will start as themselves, casually walking along Bunkum. I honestly have no idea what the player will do in this part of the level. But at some point, something clicks the player's Sackperson to go against the player.

The player will then become either Oddsock, Toggle, or Swoop in an attempt to stop the player's Sackperson from their evilish craze. The player could cycle through the three characters, all while avoiding the player's Sackperson's attacks.

Maybe even a final boss phase? 

This is just a rough idea of a level, it may have even been made before. I honestly don't know, just a 4 AM thought.

LightningAshes gone evil

Sounds like it would be a neat minigame if there's less emphasis on story and no prelude to it. It could be a cool hazard-dodging survival challenge where you swap between the three characters.