Nurse Joy is not just one person; many Joys work as nurses across the various regions of the Pokémon world. As a rule, Nurse Joys are kind, earnest, honest Pokémon nurses who take care of sick and injured Pokémon, but will confront a Pokémon Trainer if they are not properly caring for their Pokémon.
They are not entirely identical, though aside from themselves, it seems that Brock is the only one who can tell them apart. However, each Nurse Joy will have a different color cross on her hat that indicates which location she works at.
Supposedly, they are all extremely similar-looking relatives-cousins, sisters, etc. However, fans have proposed various other theories has been suggested for the strange phenomenon—everything from time travel, to cloning, to the Nurse Joys being Pokémon themselves.
There are several notable Nurse Joys who appear vastly different from the others. A Nurse Joy acts as the Pokémon League inspector in Showdown at Dark City, her first appearance as anything but an ordinary Nurse Joy. Another Nurse Joy living in the Orange Archipelago has made her career instead be as an archaeologist, leading an expedition to a deserted island in Shell Shock. A muscle-bound, kayak-riding Nurse Joy who also lives in the archipelago was featured, along with her befriended giant Magikarp, in The Joy of Pokémon. Other Nurse Joys living on the islands have a noticeably darker skin tone than their mainland counterparts, likely due to living in a more tropical region.
A Nurse Joy who appeared in The Joy of Water Pokémon was in charge of a Pokémon Center which specialized in Water-type Pokémon, despite being afraid of them herself. Two young Joys, named Marnie and Paige, appeared in Drifloon on the Wind, where it was revealed that Joy is the surname of the family, rather than the given name of each individual woman. Their mother, of course, was an ordinary Nurse Joy.
Nurse Joy, like Ash, received a redesign when the Best Wishes series began, as well as a change of clothes. All Nurse Joys in Unova have this new design. Although there are many exceptions, Nurse Joy will generally have Chansey in Kanto, Johto, Hoenn, Sinnoh, and the Orange Archipelago, and Audino in Unova to assist her. Chansey's evolution introduced in Generation II, Blissey, also appears on occasion.
There is a similarity between the families of Nurse Joy, Officer Jenny, and Don George. Fans have speculated about some sort of relation or deeper connection; however, the only thing known for sure about the three families is that they are on good terms.
Nurse Joys give out starter Pokémon to Trainers in towns or cities without Pokémon Professors, such as Slateport City. Adhering to their role as government workers, they are also inspectors for the Pokémon Inspection Agency, grading Pokémon Gyms.