Pokémon Stadium

Pokémon Stadium is a starter stage in Super Smash Flash and Super Smash Flash 2, home to Pikachu, Jigglypuff, and Mewtwo.

In Super Smash Flash
In Super Smash Flash, it is one of the six default stages and it appears similar to Melee's Pokémon Stadium, but it does not change terrain at any given time. It is the fifth stage in Adventure Mode where the player fights three Pokémon according to the ones they unlocked, which after beating the three Pokémon, a giant Pokémon will appear for battle.

In Super Smash Flash 2
In Super Smash Flash 2, the stage returns, but now its appearance will be similar to Brawl's Pokémon Stadium 2. It is still home to the characters mentioned above. It is unknown at this time if this time the stage will transform. It is also unknown whether there will be pokemon representing the stage walking about or any hazards pertaning to the stages it transforms into.

Origin
A stage such as this has never been seen in any Pokémon game. There have been flat areas where trainers would do battle, but they were always inside buildings called 'gyms'. There have been some outside areas, in stadiums such as the one seen here, but the battle area was always on the ground, and never suspended in the air. The two floating platforms have never been seen, either. There have been gyms with a theme based on a Pokémon type, such as rock or electric, and the scenery would change to match the theme. However, the exact arrangements in this stage have never been seen in a Pokémon title. A possible source of inspiration for both this stage and its Melee Stage predecessor is the Pokémon anime television show, in which type-transforming arenas featured during the Pokémon League.