Board Thread:General Discussion/@comment-29383531-20200427163918/@comment-27045866-20200427174336

The closest thing to that other than a slime would be the doppelganger, which seems to be limited to taking the form of a persons unrequited love and taking their place by showing interest in you in the ways the person you love didn't. A specialized slime like the Shoggoth could also fit, considering they can make objects and furniture out of themselves.