Event 5: Become the Champion!
From SmashWiki, the Super Smash Bros. wiki
Become the Champion! (めざせ！チャンピオン, Be the Champion!) is the 5th solo event match out of a total of 41 in Super Smash Bros. Brawl. In this, the player plays as Pokémon Trainer and must defeat another Pokémon Trainer in a 3 stock battle to become the "Pokémon Champion". The opponent rarely changes Pokémon, and a different Pokémon will respawn each time the opponent is KO'd. If one of the Player's Pokémon gets KO'd, it cannot be used again.