Board Thread:Roleplay/@comment-24947676-20160512083354/@comment-24947676-20160512085837

However, in the previous timeline, Crystal used time stop to get past the ruins without being seen by anyone (due to Demonic going Genocidal Maniac Mode), so logically, Toriel never met Crystal in the previous timeline.

But wait, them having their memories of the previous timeline doesn't make sense because Flowey had the reset ability before Frisk, and Flowey could actually erase memories of previous timelines.