i once talked to my friend how i discovered undertale and my first encounter with the game is somewhat blurry, but i remembered that what hooked me was actually a youtube animated video of sans fighting gaster with the music echo

this one

me who had like 0.1% knowledge at the game thought this is probably the main story but what made me wonder was that there's no human (frisk) that i always see in other undertale-related media

so what first came in mind is like "holy crap did this kid got cursed underground by the witches from the surface and was rotting and became a skeleton and that tall skeleton (papyrus) is their older sibling who's lost"

then i thought "that big bad scary gooey monster (gaster) killed all of their monster families and friends, so evil, but this rotten human came to kill the bad bad guy "

idk if theres any au like that, please let me know if it does exist LMAO