From Bulbapedia, the community-driven Pokémon encyclopedia.
Miyamoto flashes his well-known smile
Shigeru Miyamoto (宮本茂, born November 16, 1952) is a world-famous video game designer and creator, known as the man behind two of Nintendo's most well-known franchises, Super Mario and The Legend of Zelda. He has worked on literally hundreds of games since joining Nintendo, including being behind the initial development of the Pokémon games.
While Satoshi Tajiri had created the idea for Capsule Monsters with longtime friend Ken Sugimori, when the idea for the game was pitched to Nintendo it was rejected initially. Miyamoto, however, took interest in the idea, and over the next five years, Game Freak, alongside Creatures, another Nintendo developer, created the first Pokémon games, Pokémon Red and Green.
Miyamoto's vision for the series was a phenomenal influence, with the idea of paired versions being his own. Rather than have a single game, to emphasize the trading aspects, players would have to link up with a friend to achieve the ultimate goal of catching them all. For this, the main rival of the Generation I games and their remakes has "Shigeru" on his list of default names, while his anime counterpart is directly named "Shigeru", in Miyamoto's honor.
Pokémon cameos in other games
In Yoshi's Story, two levels, Jelly Pipe and Torrential Maze, are made from newspaper clippings. The word "Pikachu" can be seen among them, but only in certain areas.
In Mario Artist: Paint Studio, an official picture features someone drawing a silhouette of Pikachu.
In the Animal Crossing series, one of the many items that a player must collect for his or her neighbors is a Pokémon Pikachu 2 GS, though it is simply called the Pokémon Pikachu in the game.
In the Zelda series, the Keaton Mask introduced in Ocarina of Time bears a strong resemblance to Pikachu, especially in its ears and coloration. The game mentions that the mask "has been really popular lately", a likely reference to Pokémon, as Ocarina of Time was released in the same year that Pokémon Red and Blue and the anime were released in the US, as well as the same year that Pokémon Yellow was released in Japan.
In the Mario series, one of Super Mario Galaxy's many galaxies, the Buoy Base Galaxy, features a Poké Ball-shaped planet that contains a Power Star inside.