Rex can be unlocked by winning the Weekend Tournament, a certain number of times. The player can Duel him at the hometown on Mondays and Saturdays, the Coliseum on Tuesdays and Thursdays, near the shopping district on Wednesdays and the K.C. Tower on Fridays and Sundays. He also faces the player in the K.C. Tower Tournament and is a potential round two opponent in the Sugoroku Tournament.