Mouser (Mario Party Advance)
From the Super Mario Wiki
“We shall meet again.”
Mouser is a Little Mouser from Mario Party Advance, and the owner of the Duel Tower. When the player first enters the tower, he is greeted by Mouser, who then asks if they know player about the "duelist greeting" or not. If the correct answer is given ("Chaaaaarge!"), then the Duel Tower quest starts.
As the player treks the first and second floors and fights Whomp and Salvo respectively, Mouser appears between stages to cheer the player on. On the third, Mouser himself is fought. Once he is beaten, he says that only the player can stop Bowser from conquering the world, and lets him keep the tower mini-games.