Board Thread:Questions and Answers/@comment-33646122-20171224073704/@comment-28974149-20171227051254

The most likely theory as that they are halves of Gaster, who was shattered across TIME and SPACE in many different ways according to accounts and who act like the two halves of a severed brain and Sans for example, who has a half a set of eyes when glowing (interestingly, the Gaster Blaster firing animation involves it splitting in two while it's eyes glow, then one eye light sup, left for sans, and right for Papyrus,). Matpat got it right according to all game evidence. (Except for the whole Sans and Alphys being lab assistants somehow thing. Nothing states Sans and Alphys worked together and all the text in the true lab is written by Alphys, she writes in lowercase when nervous and it's all from her point of view. Now Sans would be the one to have all of Gaster's things so it makes sense he'd know her if she wanted to use the DT extractor and other Gastertech. And saying the Hyper Goner was invented by Gaster, it was not, it's a modified Gaster Blaster, Asriel did absorb Sans and Papyrus' souls after all, he'd have acess to their powers. Flowey is not connected to Gaster. But he and Sans' relationship are a part of the mystery. )