Board Thread:General Discussion/@comment-27524978-20160210030742/@comment-4383275-20160331212209

Invader Jib wrote: XFlameDroid wrote: does sans remember resets? Technically, no. However, technically everyone does at least a little-Sans just knows these vague memories are from actual timelines.

Yes, he does. In the Genocide Run, he tells the player not to talk about this "to the other Sans-es," meaning the versions of Sans from different playthroughs.