I can't believe I didn't think of this one first, and I absolutely love Kingdom Hearts.

A Nobody is an entity that is created when a person loses their heart. Some Nobodies resemble the person who lost their heart, and often their name is a rearrangement of what their real name was, but with an X added in. Sora, who lost his heart temporarily in the first game, had a Nobody created that gained the name "Roxas," who plays an important role in the games following the first one.