Welcome to Undertale Theorys, where we talk about several possible theorys for Undertale and its AUS. To start this off, let's do a fairly simple thing that Undertale fans have been wondering: Who are Frisk's parents? And why did she climb Mount Ebbot?
Well, there is a fairly simple explanation for this. Perhaps Frisk is sort of like Heidi. Her parents died, so she was sent to live with a relative on the mountain. But as she would be sent alone, Frisk got lost and fell into the underground. And as her family member did not know she was coming, they never looked for her.
This explanation may sound vague, but better ones will come soon. Sorry for the shortness of the chapter!