Sans, a major character in the cult indie game Undertale, will appear as a playable character in Pop'n Music.

The iconic lax skeleton, Sans, from Toby Fox’s Undertale is joining Super Smash Bros. Ultimate as a DLC Mii Fighter costume ...

Everhood was inspired by Undertale, but it's far from a copy -- it's more of a response to its treatment of characters, and what it means to kill in a video game.