The original Western Pokémon Stadium could use all 151 species from Pokémon Red, Blue, and Yellow.
Pokémon Stadium was a Nintendo 64 strategy game focused on three-dimensional battles. Players could use Pokémon imported from the Game Boy games through the Nintendo 64 Transfer Pak, or use Pokémon with predetermined movesets supplied by the game.
The number is easy to confuse with the Japan-only Pocket Monsters Stadium, an earlier 1998 release that supported a much smaller selection of 40 Pokémon. The Western Pokémon Stadium was based on a later and expanded version, allowing the complete first-generation roster.
The game included four Cups, Gym Leader Castle, minigames, and a Pokémon Lab for organizing compatible Game Boy Pokémon. After completing major challenges, players could unlock a battle against Mewtwo. In Japan, the expanded game was released on April 30, 1999; Western releases followed in 2000.