Not to mention Toby Fox, the creator of Undyne, worked on the soundtrack for Pokèmon. Vaporeon is a Pokèmon. : r/Undertale

Undertale Creator Toby Fox Is Composing Music for Pokemon Scarlet and Violet - IGN

Not undertale related, but apparently Toby Fox was the composer for the new Pokémon game : r/Undertale

Undertale Creator Toby Fox Discusses Composing Music For Pokemon Scarlet/Violet's Terastal Raids – NintendoSoup

I dunno what to say : r/Undertale

Undertale Creator Toby Fox Composed A Piece Of Music For Pokemon Sword And Shield – NintendoSoup

Pokémon Scarlet & Violet Will Feature Music From Undertale's Toby Fox

Undertale creator Toby Fox's Pokémon Sword and Shield song sounds like a Homestuck fan tune - Polygon

Toby Fox is making MORE music for Pokémon! : r/PokemonScarletViolet

Undertale Creator Toby Fox Is Composing Music for Pokemon Scarlet and Violet - IGN