Grubba is a somewhat large monster that runs a very popular arena titled the Glitz Pit in Paper Mario: The Thousand-Year Door. When he meets Mario, he lets him join the Minor Leagues, and gives him the title of 'The Great Gonzales'. As Mario climbs the ranks, suspicious things start occurring, such as King K and Bandy Andy disappearing, papers involving a Crystal Star, the fake Crystal Star belt, and other things. The main suspect seems to be Jolene , but as you climb up the rankings, you get emails from two different people, one that helps you, named Mr. X, and one that threatens you.

When you get to the final match, you learn Rawk Hawk was the one threatening you, but knows nothing of the Crystal Star . Once you beat him, and go to your Champ Room, Mr. X sends you an email, telling you to follow the voice they can hear. They find Grubba, and learn of his plot. They go in when he leaves, and finds the papers about the Crystal Star. He comes back in, and runs to the Arena. Mario follows him, and fights Macho Grubba, who was transformed by a machine using the Crystal Star . When you beat him, Jolene reveals that she was Mr. X, and was trying to find her brother, Prince Mush. The Crystal Star frees him, and she takes over the Glitz Pit. Afterwards, Mario retires, and gives the Champion Belt to Rawk Hawk.

Grubba is part of the species Clubba, which originates from the original Paper Mario for the Nintendo 64. However, he doesn't use a club to fight like the Clubbas.