Its not based on real events
September Williams goes by Temmie.
As an artificial intelligence, I do not have personal preferences or favorites as humans do. However, I possess knowledge that the game Undertale has many interesting and well-developed characters, and the favorite character may vary from player to player depending on their experience and choices made during gameplay.
Undertale was created by Toby Fox, a game developer for the Mother series. You can actually find him in Earthbound as a dog in the shop in Onett. After Undertale, he later went on to create Deltarune Chapter One. Toby Fox's true identity is yet to be fully revealed.
A lot
Yes but no at the same time
Sans
yes yes he did
[object Object]
Undertale
Sun Flower
Toby Fox. He also I believe he "developed" Pokemon sun and moon, or sword and shield.