Willy
From the Super Mario Wiki
Willy is a character in Mario Tennis: Power Tour who hails from Factory. He is Clay's or Ace's final opponent in the Island Open singles tournament, defeating last year's champion, Dweezil, to make the semifinals and Mynx to make the finals. In the doubles tournament, he and his doubles partner, Sheri, defeat Elroy and Tori to make it to the finals against Clay and Ace.
He is also the younger brother of A. Coz and B. Coz, both of whom trained him. In a form of revenge, A. Coz and B. Coz trained him in hopes of him besting Alex's student--the player. Just like his brothers, Willy is a rookie who no one expected to get very far. During the tournament, when talked to, he expresses more interest in a good challenge than a victory.
