From Bulbapedia, the community-driven Pokémon encyclopedia.
Kouichi Ooyama, (Japanese: 大山 功一 Ōyama Kōichi) born 1960, is one of the original game designers of the Pokémon Trading Card Game, and more recently Pokémon Duel. As well, he was the illustrator for What's Nassy's Favorite Word?. He also worked on EarthBound as an art director, graphic designer, and game designer.
He made a cameo in the Pokémon Trading Card Game video game as a Pokémon Card researcher, Dr. Ooyama (Dr. Mason in the English version of the game). Dr. Ooyama looks like Ooyama, but with gray hair, a lab coat, and a Pokémon Card attached to his head. Kouichi Ooyama has appeared at the Tropical Mega Battle in costume as Dr. Ooyama.
In the TCG
Kouichi Ooyama has illustrated various things for the Trading Card Game, such as the insert included with the Japanese 's Pikachu. He illustrated the Ooyama's Pikachu card, being credited as "Ooyama." It features a drawing of Ooyama where the Pokédex entry usually is. He was credited as "Dr. Ooyama" for the illustration of the well-known "bilingual" Exeggutor card, which had its text printed in both English and Japanese. Like Ooyama's Pikachu, it features a drawing of the illustrator in place of the Pokédex entry, who is in this case "Dr. Ooyama." For the complete list of cards that he illustrated, go here.