Who Is Gaster in Undertale Game Theory?


Vincent White

Undertale is a popular indie game developed by Toby Fox that has gained a massive following due to its unique storyline and characters. One of the most intriguing characters in the game is Gaster, who is shrouded in mystery throughout the entire game. In this article, we will delve deeper into who exactly Gaster is and what his significance is in Undertale.

Who Is Gaster?

Gaster is an enigmatic character that is introduced in Undertale through various hints and clues. He was the former Royal Scientist before Alphys took over the position, but his fate remains unknown. The only evidence of his existence comes from a few scattered notes and files found throughout the game.

Theories Surrounding Gaster

There are numerous theories surrounding Gaster, with fans speculating on everything from his backstory to how he fits into the larger narrative of Undertale. One theory suggests that he was experimenting with time travel, which led to him being erased from existence. Another theory proposes that he may have been involved in creating Sans and Papyrus, two beloved characters in the game.

Gaster’s Appearance

Gaster’s appearance is also subject to interpretation since there are no official images of him in-game. Some fans believe that he may be related to Sans and Papyrus due to their similar clothing styles. Others suggest that he may resemble a skeleton or a monster due to his connection with science and experimentation.

Gaster’s Theme

Despite not having an official appearance in-game, Gaster does have a theme song titled “Mystery Man” that plays when encountering certain anomalies. The song has become incredibly popular among Undertale fans and adds to the overall mystique surrounding the character.


In conclusion, Gaster remains one of the most mysterious characters in Undertale despite not having a significant presence in-game. His backstory, appearance, and significance continue to be a topic of discussion among fans, adding to the overall intrigue of the game’s lore. While we may never know the full story behind Gaster, the mystery surrounding him is one of the many reasons why Undertale has such a devoted fan base.