What if Chara and Frisk get stuck in Gravity Falls? Just read for explanation.

Papyrus and Sans appear in Beach City, due to universe breaking logic, and they meet Steven Universe of all people. After Steven decides to introduce the skeleton brothers to his family of holograms with mass, misadventures occur as Papyrus and Sans create antics for the Crystal Gems and Steven. Most of these involving horrible puns and spaghetti.