Nurse Joy (Japanese: ジョーイJoy) is the name of multiple nurses that work in Pokémon Centers throughout the various locations in the games and in the anime. A Nurse Joy can heal any Pokémon to perfect health. She has appeared in Pokémon Games since Generation I.
In the Anime
In the anime, the reason that Nurse Joys are all over the place is because they're all related. Not only that, Joy is their family name and not their actual first names. (Along with them looking identical, they are also all voiced by the same person, making them sound identical too)
Although they all appear identical, Brock is able to tell them apart by little details. This is noted when he can tell the difference between the eyelash length of two different Nurse Joys. Brock has a main crush on Nurse Joy, although he's always interrupted by his Croagunk, Max, or Misty. Nurse Joy is actually one of the few girls in the anime that does not reject Brock. She will just look at him, confused, before he is pulled off by one of his friends.
Once, during DP, Brock was put under a sleeping spell and dreamt that Nurse Joy and Officer Jenny fell in love with him. They then clung to him for the rest of the episode. At the end of the episode, dozens of Nurse Joys and Officer Jennys rushed over to Brock to "love" him, but Brock was then woken up by Croagunk.
Nurse Joys are known as caring women who always help a Pokémon in need. However, although they may seem nice, they can become quite tough when they have their hands full, or when they confront a person who hurts Pokémon (aka, Team Rocket). Other than that, all Nurse Joys seem to be in a good mood all the time.
Each Nurse Joy can be told apart by the color of the plus on their nursing cap, just as Officer Jennys can be told apart by the badges on their police officer caps.
In the Game
A Nurse Joy is placed inside every Pokémon center in every town, in every game. She is always behind the Pokémon center, waiting for a new customer. When you approach her and talk to her, she will say, "Welcome to the Pokémon Center, where we will heal your Pokémon back to full health. Would you like me to take your Pokémon?" If you click no, she will say, "We hope to see you again," but if you click yes, she will say, "Okay, I'll take your Pokémon for a few seconds." She will then take each of your Poké Balls and place them on a tray, where they will light up numerous times before Nurse Joy takes them and hands them back to you. She will then say, "Your Pokémon are now healed. We hope to see you again." On your birthday, she will ask you if it is your birthday and she will wish you a happy birthday. She will also say a little bit of Pokerus if your Pokémon has it or was cured from it.
This phrase has gained a lot of jokes to it, due to the fact that Nurse Joy says, "We hope to see you again," making it sound like she wants your Pokémon to get injured again so that the player would have to go back to the Pokémon center.
In the anime
Nearly every Nurse Joy in the anime have Pokémon with them at some point in time.
The Bulbasaur was one of the Mayor's Bulbasaur when he was a kid but was released because it wouldn't evolve. It was later found in the sewers by Ash, Tracy, and Misty which got the Mayor fired. It was later given to the Pokémon Center so it could have a home.