One day after school, Sweetie Belle, Apple Bloom, and Scootaloo head to their clubhouse just like any other day. Today, however, they find a mysterious grey door has appeared in the back. Curious, they open it, finding nothing but a deep darkness inside. When Sweetie loses her balance and tumbles through, the other two dive in after her, beginning their new adventure across the multiverse in order to find their way home.

Deltatraveler by RynoGG
Undertale and Deltarune by Toby Fox
Undertale Yellow by Team Undertale Yellow
TG!History Recast by TGMoonrose (that's me!), inspired by Andoro-T and Brenny114's History Recast
The Legend of Zelda series by Nintendo