Overgrown Rover (育ちすぎたポチ, Sodachisugita Pochi; Viz: Overgrown Pochi), also called Rover, is a Dragon-level Mysterious Being and an executive member of the Monster Association. Its role is to guard the Monster Association Headquarters.

Rover is a very large, black, six-eyed dog monster. Its eyes are ruby colored and seem to have a glow. It has very large fangs and four toes per paw. Its fur is very shaggy and roughed up, especially on the outer part, whereas the inner part of its body presents less hair and shows clearly its muscles. It lacks a tongue, and has no visible ears or nose.