Kapoerer's Trainer

Mason is a character of the day who appeared in Outrageous Fortunes (EP249). He was unnamed in the Japanese version.

Mason was the seventh consecutive Trainer to battle Delaney. He hoped that his Hitmontop would be able to put an end to Poliwrath's winning streak. However, Delaney proved to be more powerful and defeated the young Trainer's Fighting-type Pokémon.

Mason is named after his English dub voice actor, Mason Ripka, who was one of the many kids who got to cameo in the show as an extra.

(Source: Bulbapedia, edited)