Doppelgängers

Note: This is almost always spoiler tag.

Japanese folklore/mythology is rife with creatures that pretend to be humans. The name of this tag however is from European folkloristic changelings, creatures (usually trolls or such) or objects placed in stead of human child that fooled at least their parents into thinking it was their real child, usually with the purpose of raising the child at expense of the human parents. However, this tag is more extensive than that, covering "monsters" and other beigns disguising themselves as humans for both malicious and even benevolent reasons (the actual reason for the subterfuge is not covered by this tag).

See also: simulacrums, alternate self, shapeshifters, mimics