Presumably in this timeline his soul is in a different place than his friends. Which brings us back to undertale. 3 faces, with “don't forget” written on it? Its ness, trying to remember his 3 friends. In short, undertale is a continuation of toby’s version of earthbound, with ness never being able to get home, adopting the name sans, and being accompanied by papyrus, a starman, with knowledge of english, his armor, and his signature posture, but without any of his memory of human things, like the sun. The pieces all just seem to fit. Now all we need is an appearance from Pokey/Porky and we’d have a true sequel. But hey, that's just a theory. A GAME THEORY! THANKS FOR WATCHING!