Well, it could be that the Pokemon is accompanying its trainer who is sick or injured. The trainer might have had an accident while traveling with the Pokemon, like falling from a cliff (not too seriously though). And the Pokemon, being a loyal companion, goes with the trainer to the hospital. There, they might encounter other Pokemon and trainers, and there could be some interesting interactions between them, like sharing stories of their adventures or learning about new ways to take care of Pokemon's health.
In this fanfiction, maybe the Pokemon gets injured during its trip and has to be treated in the hospital. For example, it could have been in a battle with a wild Pokemon and got hurt.
There might also be some hospital staff Pokemon, like Chansey, which is known for being a nurse in the Pokemon world. They could play important roles in the fanfiction, helping the sick or injured Pokemon and interacting with the trainer and the Pokemon on the trip.
Maybe Harry is injured during a Quidditch match and has to be rushed to the hospital. There he might meet some interesting new characters, like a healer with a mysterious past.
In the 'pokemon ash in the hospital fanfiction', it could be that Ash got poisoned during an encounter with a new and dangerous Pokémon. While in the hospital, he starts to have strange dreams about a powerful Pokémon he has never seen before. His friends come to visit him, like Misty and Brock. Misty might scold him a bit for being too reckless but also show her concern. Brock could be using his knowledge of herbs to see if there are any that can help Ash's recovery. And all the while, Ash is thinking about getting back on his journey as soon as possible.
In the fanfiction, Danny might be in the hospital because of his ghost - fighting injuries. Maybe he has to hide his ghost powers from the doctors while trying to recover.
In fanfiction, when Naruto goes to the hospital, he could discover a new medical jutsu being developed there. He might get involved in the process, either by accident or because the doctors need his help. Since he has so much chakra, it could be useful for testing or something related to the new jutsu.
In a hospital Pokemon trip fanfiction, Pokemon could engage in unique interactions. Some Pokemon with psychic abilities, like Alakazam, might be able to sense the distress of patients and communicate that to the medical team. Smaller Pokemon like Jigglypuff could sing lullabies to put patients to sleep. And Pokemon that can fly, like Pidgeot, could deliver messages between different wards quickly. Their presence would add an element of magic and comfort to the often sterile and intimidating hospital environment.
Well, in such a fanfiction, perhaps Pikachu might be on this pokemon trip and confess its deep friendship and loyalty to Ash. It could say how much Ash means to it and how their adventures together have been the most important part of its life.
In this fanfiction, perhaps May and Drew are both in the hospital after getting caught in a strange Pokemon - related incident. They could start to realize their feelings for each other while recovering. Drew might share his dreams with May, and May could open up about her insecurities, strengthening their bond.
In the hospital setting of a fanfiction, trainers would interact with their Pokemon in different ways. Some trainers could be using their Pokemon as emotional support for themselves while they visit sick friends or family. A trainer with a Snorlax might just sit beside it and feel comforted. Others would be guiding their Pokemon to do good deeds. For instance, a trainer with a Psyduck could be trying to get it to use its water - based attacks in a controlled way to help clean up small messes. Trainers would also be teaching their Pokemon proper hospital etiquette, like not running in the hallways.
In the 'Harry goes to the hospital fanfic', it's possible that Harry is injured during a Quidditch match. He is then rushed to the hospital. There, he could discover a hidden part of the hospital that has some ancient magic stored. He might also have some deep conversations with his friends who come to visit him about their future plans and the current state of the wizarding world.