Board Thread:General Discussion/@comment-27524978-20160210030742/@comment-27701762-20160401043019

In order for that to work, Sans would need to retain memories across not just normal resets, but True Resets. Otherwise, the entire concept of him "distinguishing" between a Neutral version of Frisk and a Genocide version would need to be built upon the player completing a Neutral route followed by a Genocide route.

When he gets violent with Frisk, Frisk has definitely eliminated a huge number of monsters. So at what point is Sans getting violent with a child who "might just be stoic?" In fact, Frisk isn't actually "stoic" in the game, except at a few points in the Genocide run. That the sprite does not show emotions does not mean that Frisk is always blank-faced the entire time. Just as the fact that Frisk's mouth never moves does not mean that they never speak.

My entire point is that every single line can be explained just as well by a basic assumption that Sans has the exact same vague sensation of something having occurred in another timeline, akin to Toriel's remembering your choice between cinnamon and butterscotch, and Papyrus and Undyne getting the feeling like they know you already. They don't actually remember what happened in the other timeline. They just have an impression of it, just as we would describe the sensation of deja vu. Sans's reactions can be explained in the same way, except he has an awareness that these impressions aren't random or coincidental, but the effect of someone messing with the timelines.

Flowey is an example of someone who actually remembers events. He knows when you abandon the game versus get killed. Perhaps as a useful comparison, if you exit the game in the middle of the Sans fight, he treats it as though he killed you, when in fact he hasn't. If he has an actual memory, why doesn't his reaction change? Given that Flowey clearly has actual memory of the resets and Toby took the time to differentiate between those two actions, why would he not do the same for Sans if he remembers just as Flowey does?

Given that not only Sans, but many characters react to your facial expressions in the game, I don't see why it has to be so implausible for Sans to read your face as a way to knowing how many times you've died, or that he's killed you before.