At that moment, an alarm in the Pokémon Center sounds and a villainous group named Team Rocket invade the building. Their Poké Balls break a skylight, and Koffing fills the air with smoke. Team Rocket recites their motto for the first time to Ash and destroys the Center’s electrical system in a scheme to steal the Pokémon inside. Nurse Joy, Misty, and Ash retreat to a locked storage room with Pikachu, who is still on his stretcher. The power initially cuts out, though the backup system, Pika-Power, activates. Nurse Joy begins transporting as many Pokémon as she can to Pewter City’s Pokémon Center. Suddenly, Koffing breaks through the doors. At Misty’s insistence, Ash tries and fails to fend off Ekans and Koffing with a Pidgey, an empty Poké Ball, and Rattata. Misty calls on her Goldeen to help, but without a body of water in which it can swim, it flails helplessly before being recalled.
(Source: Bulbapedia)