Board Thread:Questions and Answers/@comment-24800939-20161004020532/@comment-61022-20161004135832

That, my friend, is a very complicated question! To which there is no official explanation, but situations like this have happened before (notably in -) and my assessment is this:

When someone causes a reality warp that changes all of reality, one reality is overlaid with the other. Analogous characters are "merged" together wherein while they appear physically one way, memory of the old reality still exist in their mind. It takes some outside force to awaken these memories so that an individual remembers both realities.

So technically speaking, both versions of the character exist simultaneously and occupy the same body and space in one physical form but with two minds.

So using House of M as an example: The Scarlet Witch caused a reality warp that replaced Earth-616 with Earth-58163. Prior to that point Earth-58163 presumably did not exist (since when one reality is replaced with another the going rule is that it is never with a pre-existing reality). When the Scarlet Witch created Earth-58163 it "wrote over" Earth-616 because she altered reality using elements of what already exist.

Ergo, the Wolverine of Earth-616 was "written over" with his new Earth-58163 counterpart. However, the memories of the 616 Wolverine and knowledge of the "proper" reality still existed in his mind.

When Wanda restored reality to mostly-normal, the elements of what became Earth-58163 were removed from Earth-616 and became it's own independent reality.

What they never really explain (I think, someone correct me if I am wrong on this) is if the individuals in the dominant reality remember what happened. Like does Wolverine of Earth-58163 remember what his 616 counterpart was doing when he was in control of his body?