Sans has definitely noticed that his other self seems especially pensive. It's not a good look on him. Yet when he stops to think about it, it's not hard to guess why. Between their encounter with Croc and everything that happened after...he was too busy getting caught up in a Chara's idea of fun, but it's not hard to imagine that other Sanses probably had an equally or even more miserable time of it.

"yo." He blinks into place leaning against Sans' chair as well, a half-eaten muffin still in one hand. "thanks for stopping by."