Gaster

"I have to find some way to stop them! But how… I can only maintain my physical form for a few seconds.. Wait! What if I can find one of my soul shards.. Then perhaps I can manifest for longer! (pause) Now let’s see… there should be one in my old lab here somewhere… Gahah! There it is! Alright, I need to time this correctly.. If I fail to succeed then this could mean the fate of the universe will be a horrible nightmare."

(taunting) "Haha! Oh come now, child. Isn’t it obvious? The red eyes? And you look exactly alike. It is obviously you. I cannot believe they were all so thick-skulled to not see it."

(pessimistically, matter-of-fact) "Oh child, there is no way of me returning to your world. I am trapped here to atone for my actions."

(curious) "Wind Dings you say? I created that language, give it here."

(realization) "Yes… yes, of course! Why didn’t I think of it before?! Since my soul was shattered the pieces had to go somewhere, right? Turns out they’re all nestled within our own reality! I thought it was only the one, but… of course! Why would the rest go anywhere else?!"