Pokémon Change is a move performed by Pokémon Trainer by using his Down Special Move. This move allows the Pokémon Trainer to swap out his current on-stage Pokémon to a different one. When switched out, the current Pokemon tags the next in the trio, who then continues fighting. The Pokemon still share the same damage meter, but they also have a new special stat, called Stamina. If a Pokemon is on the field too long, or they are switched out too often, penalties occur, such as slower movement and weakened attacks.
The order that the Pokemon follow when Pokemon Change is used is as follows: Squirtle, Ivysaur, then Charizard. If Charizard is on the field when Pokemon change is used, you will switch back to Squirtle.