Board Thread:General Discussion/@comment-26006155-20200107155350/@comment-26006155-20200124205654

No smoking gun about Sans remembering things between runs yet.

I did learn that Papyrus remembers the bag of dog food in Alphy's lab was once in Sans' room: And Sans definitely doesn't add to the kill count in Stats, and the game doesn't record whethere or not he's killed. I imagine he isn't.
 * ↑ "WAIT... THAT BAG OF DOG FOOD LOOKS FAMILIAR. I REMEMBER SEEING IT... IN SANS'S ROOM?" – Papyrus, on the bag of dog food in Alphys's lab.

I still find it amazing, though, that Sans is able to reliably read how many times we've died to him, just by our facial expression. And he only seems to mess up around 9... but actually doesn't, always getting it correct by the end.

We tell Asgore how many times he's killed us. And Sans tells US how many times he's won.

And Sans is aware that we have a special power, and isn't surprised at all that we can travel in time, seeming to intimately know just how Saves and Loads work.

Theory about him being human isn't confirmed, but it isn't debunked, either.