Fan Casting Empty Shell in Sort by Tropes

This character is... barely a character. For many reasons, they've gone past the Extreme Doormat and Stepford Smiler and become nothing. They aren't a pushover or empty of real personality, they are completely dead inside. They are this side of a Convenient Coma because there is still something there — they move, talk, eat, sleep — but they have no drive, ambition, or capacity for emotion. Basically, the body is an active biochemical machine, but the part that made them alive and human is gone.