what is a shape changer?

Answer 1

A shape changer is usually a Shaman type, who is assuming the form or aspect of an animal. Usually it's an animal either sacred to the shaman, or is a guide or totem animal of the shaman.

This is not to be confused with the idea of Were creatures, which usually has an uncontrollable aspect to it, or an allowing of the Beast or animal side of human nature to dominate...

Answer 2

there is a microbe called a "water bear" and it changes shape

perhaps you mean Odo from Deep Space Nine?
He was an ontologically dynamic object

Answer 3

morpher???