The charizard v. charizard duel at the climax of the creatures cup is all but completely explainable in Pokémon Red and Blue game mechanics: both charizard used the Rage technique against each other. Rage causes its user to enter a cycle of perpetual attacking until the battle is over, with each attack the user receives in turn causing them to grow stronger.
technique against each other. Rage causes its user to enter a cycle of perpetual attacking until the battle is over, with each attack the user receives in turn causing them to grow stronger.