Any Scary Topic/The Mandela Effect

In this final episode of October Pet Spooktacular, any scary topic goes.  Ghosts, monsters, aliens, cryptids.  You name it, we can go there.  Plus we'll be discussing the phenomenon known as The Mandela Effect.  Have you ever sworn that you can remember a set of facts or circumstances being one way, only to find they've now somehow changed?  For instance, some people remember Mandela dying in prison in the 80's, while others remember him the way current history portrayed his life.  Then there's the Berestain Bears controversy: Some clearly remember it as being spelled Berenstein, while others remember it as always being spelled Beren"stain".  Why are so many people having such differences in memory?  Is it a normal error in our mental processing or have some of us slid into other dimesions where history unfolded differently from how we remember things?