Despite having the title "Nurse", Nurse Joy actually is what a veterinarian is in real life, she is only outranked by Pokémon Doctors.
The actual proper title for “Nurse Joy” is actually Pokémon Nurse (PoN).
Due to the excruciating difficulty of the exams, only few people take the additional time to study at Universities to become Pokémon Doctors, or even passed them. Still, Nurses make up 60% of Pokémon Doctors.
A Nurse is required to take basic first-aid courses for humans and self-defense classes.
When in the military, Nurses must also undertake special training against psychic attacks.
The Joy's family crest is a Chansey.
Attacking a Pokémon Center is considered terrorism.
A Nurse is the last one to leave the Pokémon Center in case of an evacuation.
A Nurse can take away a trainer's Pokémon in case of heavy abuse/mistreatment.
The PIA also inspects Pokémon Centers (under much stricter guidelines, naturally, since it's a medical facility for Pokémon).
Nurses inspect and treat the Gym Leader's Pokémon regularily, but unlike the PIA, they cannot shut the Gym down.
Nurses can and will call the PIA if something's not right in the gym.
Most Nurse Joys and Chanseys know each other since their childhood.
The Nurse school for Chanseys is near to the Nurse school for humans so they can see each other.
Nurses have their own little league and contest.
Participating in at least five Gym battles is a requirement for a Nurse, to prove they are good enough to defend the Pokémon Center in case of emergency.
The Nurse Schools for both Chansey and Humans are officially named "The Anabelle Joy School of Pokémon Nursery (for Chanseys, or other Pokémon, depending on Region)"
Annabelle Joy was the first Nurse Joy, a Pokémon Nurse who became famous after evacuating a military hospital for injured Pokémon during the siege of Viridia City during the Kanto/Johto War. As soon as the last Pokémon (Chansey) left the tent, it was hit by a stray mortar grenade, instantly killing the Nurse. The circumstances of why and how she knew of the impending attack are unclear to this day, but Annabelle Joy was considered a war hero, and in her honor, the Annabelle Joy School of Pokémon Nursery was built.