Pokémon : S5 | E33 – As Clear as Crystal

The group continues towards Blackthorn City, and Ash returns to his human self after being turned into a Pikachu by Lily's spell in the previous episode. Now one issue is solved, but Misty is furious to learn that they are once again lost in a forest. Ash manages to settle Misty before Team Rocket appear disguised in an orange and purple tuxedo. James removes the white cloth covering the PikaPower Mach II, a machine designed to restore electricity of tired Electric Pokémon like Ash's Pikachu. Jessie rips Pikachu off Ash's shoulder and straps him in. Next, she radios in Meowth who swoops down in the balloon and takes Pikachu, Jessie, and James into the sky. As they ascend, Jessie and James remove their disguises to reveal themselves. Jessie tells Ash to command Pikachu to use Thunderbolt. But the energy is absorbed into Team Rocket's machine, which also has the power to forcibly drain its victims of energy. Team Rocket threatens to sap all of Pikachu's power if Ash doesn't hand over the rest of his Pokémon, but Ash simply tells Pikachu to give it all he's got. Soon enough, Pikachu's power overloads the machine and Team Rocket goes blasting off. Ash happily catches Pikachu, but the power drain has left him exhausted.

Just then, a girl named Krystal approaches the group. Brock instantly falls in love with her at first sight. However, Ash goes on to tell her that Pikachu is badly hurt and that there isn't a Pokémon Center for miles around. Krystal offers to help but asks them to keep a very big secret for her in return, and the group agrees to the request. She leads them up a large hill. As they walk, the group notices numerous Electric Pokémon climbing up the hill - Krystal tells them that they're all going there for a special reason. When they get to the top of the hill, they find a big lake, which Krystal claims has magical healing powers; the Electric-types come here to rest and recharge. She orders Ash to put Pikachu into the water, and the Mouse Pokémon is soon good as new. After Pikachu is healed, Krystal takes Ash and his friends out to the middle of the lake in a speedboat to show them the secret to the lake's power. When they look down from the bottom of the boat, they see what looks like an underwater temple with a crystal at the bottom. Krystal informs them that the Electric Pokémon have been coming to the lake for years. She explains that according to legend, the temple sank into the water after torrential rains.
(Source: Bulbapedia)