(SORRY IF I GOT SOME FACTS WRONG!)
Once, there was a universe where the most important thing was....
a tree.
This tree, named the Tree Of Feelings, produced 2 kinds of apples. One side produced golden, glowing apples.... these represented the hopes and dreams of every living being in that universe. The other side produced dark, rotten apples. The two guardians of this tree, named Dream Sans and Nightmare Sans (or NM), protected this tree and cared for it. Dream took care of the golden side, and NM took care of the dark side. People from around the world came to see Dream's apples, whereas NM's went unnoticed. NM got so tired of being bullied and jealous.... that he tried to care for one of the golden apples. But upon his touch, filled with envy, the apple became rotten and corrupted. Dream, who was nearby, tried to stop him.... but it was too late. The apples all became corrupt.... and the townspeople noticed. NM was so terrified, being backed up against the Tree with Dream trying to stop the people from hurting him, that he took a bite of the apple.

PART 2 COMING SOON U-U