Charizard might initially be confused and a bit frustrated. It's used to Ash as he was before. But then it would come to accept Ash's new form. Charizard would be very protective in battles, using its powerful attacks to keep Ash safe. It might also try to learn from Ash's new fairy powers, like how to be more in tune with nature like fairies are.
Some of his Pokémon like Pikachu might be very protective. Pikachu would stay close to Ash at all times, being extra vigilant in case any danger comes while Ash is in this new form. It would also be curious and might try to play with Ash's new fairy features, like his wings if he has any.
At first, his Pokémon would be startled. They've always known Ash as a human. But then, they would start to adapt. Some Pokémon, like Squirtle, might try to play with Ash in his new form, thinking it's a new kind of game. However, his more loyal Pokémon, like Greninja, would be determined to find a way to turn Ash back. Greninja might use its special bond with Ash to try and communicate with him on a deeper level in this new form, to understand what happened and how to reverse it.
Some of his Pokémon might be very confused and sad. Pokémon like Pikachu, who has been with Ash for a long time, would probably miss the adventures and battles they had together. Pikachu might try to cheer Ash up and convince him to change his mind.
His other Pokémon like Charizard would be completely bewildered. Charizard might initially think that this Eevee is just some random Pokémon near its territory. But when it senses something familiar about the Eevee, it would be hesitant and curious. It could try to communicate in its own way, like using small bursts of fire to get the Eevee's (Ash's) attention. The Pokémon that Ash has a closer bond with would be more determined to figure out what's going on and how to help him.
His other Pokémon like Bulbasaur and Charmander would also be startled. They might gather around Ash - Zoroark and sniff him out to make sure it's still him. They could be a bit hesitant to follow his commands at first because they're not used to his new form. However, as they see that Ash's spirit is still there, they would gradually start to trust and follow him again, and they would work together to figure out how to turn him back.
Some of his Pokémon might be confused. Pokémon like Pikachu, who has a very close bond with Ash, would initially be in shock. Pikachu would likely try to understand why Ash is doing what he's doing and might even try to stop him at first.
Some of his Pokémon might sense the change in Ash immediately. Pikachu, being his closest partner, could be both curious and a bit protective. It might stay closer to Ash during battles, as if it knows Ash has a new power to draw from. Other Pokémon like Charizard might be a bit more aloof at first, but as they see the benefits of Ash's aura powers in battles and in protecting them, they would come to accept and rely on it.
The story would likely become more about Ash's internal struggle. As a Pokémon, he'd view the world from a different perspective. His goals might shift from winning badges to something more related to Pokémon survival or acceptance. For instance, he may strive to prove that Pokémon with human - like intelligence deserve better treatment.
Pikachu would be super excited. It has been with Ash for so long and would see Misty as part of the family. It might play more with Misty's water - type Pokémon. Misty's Starmie could be very protective of the new family unit and use its psychic powers to help around the house sometimes.
Their Pokémon would probably be very protective. Pikachu, being Ash's closest companion, would always be on guard around the baby. It might even try to play with the baby in its own cute way, like using its electric shocks to create little light shows to amuse the baby. Serena's Pokémon, like Fennekin which evolved into Delphox, could use its psychic powers to sense if the baby is in any danger or discomfort. All of their Pokémon would likely adapt their usual habitats and behaviors to be more baby - friendly, for example, making sure not to use any dangerous moves near the baby.
Pikachu would probably be very curious. It might zap the lightsaber a bit to see what would happen, and then be in awe of the bright blade. It could also get a bit protective of Ash when he wields the lightsaber, as if it senses the added danger.