The Giant Robot Ghost Monster, a giant robot at least 50 feet tall (and closer to 100 feet), was built by Mezmeron and his Ghost Monsters in order to terrorize the citizens of Pac-Land into telling them the location of the forest of trees that grew Power Pellets. The giant robot had two weapons: a set of metal jaws used for chomping attacks, and a giant horn. The Robot Ghost Monster moved along on a tank-like chasis with a pair of treads.
In the TV episode Here's Super-Pac!, Mezmeron and the Ghost Monsters pilot the giant robot and cause a path of damage and destruction in the urban areas of Pac-Land. When Super-Pac confronts the giant machine, it uses it's giant horn to blast Super-Pac into a fruit and vegetable stand.
Angered, Super-Pac gulps down on a Super Power Pellet, and the Ghost Monsters and the larger Giant Robot Ghost Monster turn purple with panick as the giant metal monster retreats despite Mezmeron's disapproval.
Super-Pac's chomping destroys the giant robot and turns the Ghost Monsters inside into disembodied eyes as their ghost suits are consumed. Mezmeron himself flees.