Melissa is a character of the day who appeared in The Fourth Round Rumble (EP079).

Melissa battled Gary during the fourth round of the Indigo Plateau Conference. Melissa was shown to be a quite powerful Trainer. As only one Pokémon remained in each Trainer's team, Melissa's Golem defeated Gary's Nidoking, sending the Pallet Town resident home. Melissa was not seen afterwards.

Melissa is male in the Japanese version, and female in the English version.

(Source: Bulbapedia)