Maybe a Jigglypuff could be in the bathroom during bath time. It could start singing its sweet song, which makes the bath time even more relaxing for the trainer. Meanwhile, a Psyduck could be splashing around, not really understanding what's going on but still having a great time. And the trainer could be sharing some bath toys with these Pokemon.
One idea could be a Pikachu accidentally getting into the bath with its trainer and having a little adventure in the soapy water. It might discover some hidden toys at the bottom of the bath that it thinks are treasures.
By giving them unique bath - related quirks. For example, Meowth could be obsessed with keeping his fur perfectly groomed during bath time, using his claws as combs. This would make him an interesting character as he scolds the other Pokémon for splashing too much water and messing up his grooming session.
One idea could be that Pikachu accidentally slips into the bath while chasing a floating Pokeball. It creates electric sparks in the water which turn the bath water into a mini electric pool, but without harming anyone. The other Pokémon gather around to see the strange phenomenon and it becomes a fun bath time adventure.
One idea could be a magical bath time. In the fanfic, the character could discover that the bath water has special powers, like making them able to communicate with mythical creatures that live in the drain. For example, they might meet a tiny mermaid who gives them a pearl as a gift.
A more complex way would be to have a portal that moves Pokemon across great distances and through time. A young trainer could accidentally step through this portal and find themselves in a strange new region with Pokemon they've never seen before. As time passes in this new place, the trainer has to figure out how to get back home while also learning about the new Pokemon and the secrets of the portal. This would create a lot of opportunities for adventure and discovery in the fanfiction.
You can play with colorful bath toys like rubber ducks. They float on the water and can make bath time more interesting.
In another family, mom started a tradition of reading a short chapter of a children's book during bath time. The kids looked forward to it every day. Dad would sometimes act out the characters in the story while the kids were in the tub. This made bath time not only a time for getting clean but also a time for enjoying stories and family togetherness. It was a really special time for the whole family.
One way is through the dialogue. Make the characters use simple words and phrases, like a child would. For instance, instead of complex battle strategies, a trainer might say things like 'Go, Pikachu! Make it go boom!'.
One way Naruto aura could be incorporated into Pokemon fanfiction is through a crossover of abilities. For example, a character might have the ability to use Naruto - style chakra, which they could then use to enhance their Pokemon's attacks. This could add a new layer of strategy and power - up to battles in the Pokemon world.
The main characters could be the angels themselves. There might be a lead angel, perhaps named Gabriel or Michael in this fanfiction. They would be the ones experiencing the bath time and all the events that come with it.