Pokémon: Indigo League

Attack of the Prehistoric Pokémon (1x46)

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Arriving at a canyon to find an old fashioned fossil hunt, Ash, Gary and the gang decide to join in. But Team Rocket arrives and intends to blow the canyon up. Ash, Pikachu, and Team Rocket fall into a pit which is full of awakened ancient Pokémon. Their only hope rests in Ash's disobedient Charmeleon, which evolves into a powerful, yet still disobedient Charizard to defeat a raging Aerodactyl. In the end, the ancient Pokémon are sealed away once more (along with a terrified Team Rocket) and Officer Jenny dismisses the entire event as a side effect caused by Jigglypuff's singing. Ash, however, finds a rare Pokémon egg in the chaos and keeps it.