When Mario, Mallow, Geno, and Bowser were chasing after Booster onto the balcony, Knife Guy and Grate Guy attacked them, but they defeated the two jesters. Afterward, Grate Guy opened up a casino in Bean Valley.
In battle, Grate Guy has 900 HP, 60 ATK, 40 DEF, 25 magic attack and 40 magic defense. He uses magic attacks Meteor Blast and Echofinder, and he is weak against thunder.
His Psychopath thought is "Peace is just a dream."