[Sans notices someone else outside pretty quickly, even distracted by his watch. He doesn't get a good look at the guy until after he's read Papyrus's message, since that's more important than whoever's next door, but then he realizes. He remembers hanging out with Papyrus more than once in October; the weird and familiar human face of his brother is something he still remembers. As for Sans's own weird human face, all those muscles make it much easier to see how he lights up as soon as he recognizes Papyrus.
no subject
...But then Sans looks back down at his watch.]
that's weird
mine's 103