Parasite

Parasites are life forms that feed off other beings in some way. In anime, they are often aliens and usually intelligent. For shock value, and to avoid having to draw aliens all the time, their prey is preferably human; they may see humans as food, as puppets for mind control, or simply as temporary body hosts. In every case, the human is the victim of a "merging", which is not to be confused with the more "amicable" symbiosis.