#1
The Badtime Trio of U.A.by SirHappiness
Sans and Papyrus were experimented on, but managed to escape from their tormentor
Chara was an anxiety filled lonely girl, with a strange love if sharp objects.
What did...
#2
The Ninja Of The Past And Present...by M10SophiaMargaretGLa
This is basically the same story except the other five didn't meet Kai and his team after they defeated the overlord but during the battle of Crystallized.