From the Super Mario Wiki
“Yikes!! They're pretty tough!”
Grate Guy is a boss in Super Mario RPG: Legend of the Seven Stars. He and his brother, Knife Guy, apparently work for Booster as bodyguards. As Booster flees to Marrymore with Princess Toadstool in tow, Mario and company fight Grate Guy and Knife Guy on the balcony of the tower.
Grate Guy is a magic user; he will either attack, use Echofinder to Silence a target (preventing it from using magic), or put the target to Sleep. At some point in the battle, Knife Guy will call for a team-up, and he will stand on Grate Guy's head. They are still considered separate targets during this time.
During the team-up, Grate Guy will use Meteor Blast every turn, inflicting strong damage to the party. This phase's length is determined by a hidden counter, as well as Grate and Knife Guy's HP. Each time Grate Guy takes damage, the counter is increased by 1, and each time he uses Meteor Blast, the counter is increased by 2. If either Grate or Knife Guy is defeated, or the counter reaches at least 5, they will separate and return to their first phase.
Later in the game, Grate Guy opens up Grate Guy's Casino. The entrance to the casino is well hidden in the underground of Bean Valley. If Mario and company have a Bright Card, the casino membership card, which they can win from Knife Guy, they may enter.
Grate Guy can play a game with Mario called "Look the Other Way". To play, Mario must guess which way Grate Guy will look, and look the other way. If Mario wins, he will be usually be rewarded with sub-par prizes such as a Rotten Mush or a Wilt Shroom and a Moldy Mush, although he will occasionally receive rare items including Red Essences and KerokeroColas. If Mario plays a hundred times, however, he will be rewarded with the Star Egg, a powerful item.
Names in other languages