The Royal Scientist

Did you guys know Gaster’s been there since the war happened?. The fact that there’s electricity power in the ruins confirms us that Gaster has been there for quite some time

He saw Chara and Asriel. And probably interacted with them

He saw Toriel leave Asgore’s side.

He build the CORE.

He pretty much started the DT experiments.

And just like it never happened, he was gone. I really wish I could get a game entirely focused on his past, even tho we don’t interact with him in the game that much, he’s such an important character in the story and I luf him.