Toby Fox

Toby Fox is the creator of the game "Undertale", as well as the composer of Undertale's series of original themes that would be the basis for many fan musical adaptations in YouTube, one of them being "Undertale the Narrator's Musical".

He would later create the game, "Deltarune", which is supposedly an alternative universe of Undertale.

Avatar Appearance
His avatar is the Annoying Dog, a white dog that would cause mischief and problems to the residents of the Underground. His crimes would include eating Toriel's pies without permission and stealing Papyrus' bones.

His avatar makes cameo appearances in both the original game and the musical.