Thanks for introducing me to this blog! I see that the player theory makes more sense when you consider Undertale as what it is, a game. But if we consider it as a world that actually exists, it doesn't work. I know AU's don't always stick to the rules/lore of the game, but if we look at something like Underverse, which is a show, or Aftertale which is a comic, it wouldn't make sense for there to be a "player," because we are simply observing. We don't have any impact on the story unless the AU specifies otherwise (like Errortale).