The phone then starts ringing; when the doctor refuses to answer, saying he is off duty, Brock answers for him and learns it is Nurse Joy. She informs the group that there has been a violent accident involving a truck of Pokémon stolen by Team Rocket, and the Pokémon are in dire need of medical attention. With the Pokémon Center at full capacity, the extra room in the hospital is needed. Instead of giving Nurse Joy a serious answer, Brock asks her out, making her angry. Meanwhile, Team Rocket is at the scene of the accident, with Jessie blaming James for the accident, while Meowth is feeling down because the charm on his head is missing. Back at the hospital, the doctor gives hospital uniforms to Ash and his friends to wear, as well as medical equipment, saying that he needs their help due to a staff shortage. When the injured Pokémon arrive on stretchers pushed by Chansey, everyone starts working. Ash calls out his Bulbasaur to hold down Cubone, who is struggling in pain. Misty then comforts it and successfully calms it down.
(Source: Bulbapedia)