Another story idea is that the Joker somehow gets his hands on a powerful and mischievous Pokemon like Ditto. Ditto can transform into any other Pokemon, and the Joker uses it to create all sorts of mayhem in Gotham. Batman has to figure out how to stop the Joker and his shape - shifting Pokemon while also dealing with other criminals who see this as an opportunity to cause more trouble.
You can try looking on fan fiction websites like FanFiction.net or Archive of Our Own. They have a wide range of pokemon fan fiction, and you might be able to find some stories that are about catching only shiny pokemon by using the search function and typing in relevant keywords.
First, make the character have a distinct personality. For example, if it's a trainer, they could be really shy but extremely determined when it comes to catching Pokemon. Their shyness could add an interesting dynamic when they interact with other trainers or their Pokemon. Second, give them a unique backstory. Maybe they grew up in a region where TF Pokemon are feared, but they have a different view.
One common theme is the struggle for freedom. When a trainer is caught, they naturally want to break free and continue their journey. Another theme is the discovery of new pokemon abilities. As they are in a difficult situation, they might observe their pokemon in different ways and uncover hidden powers.
Perhaps they are caught washing clothes in a really strange situation. For example, they are in a post - apocalyptic world where water is scarce. Kagome, being from a different time and place in her own story, has some traditional methods of washing. Batman has his high - tech gadgets for purifying water to wash his suit, and Superboy is using his super - strength to wring out the clothes really fast. And this all makes for an interesting encounter when they are 'caught' by some local survivors.
One possible scenario in this fan fiction could be that Ash has some sort of special ability or connection that attracts only shiny Pokemon. Maybe it's a hidden power within him that he discovers early on in his journey. For example, when he first starts out in Pallet Town, instead of the regular Pikachu, a shiny Pikachu is drawn to him. This would set the stage for his entire journey filled with shiny Pokemon encounters.
Well, Batman could be seen as a sort of Pokemon master. He could have a special Bat - themed Pokeball. His Batcave could also double as a Pokemon training ground. For example, he could train his Pokemon in the same way he trains himself for combat and detective work.
They could be embarrassed at being caught and try to come up with excuses. Maybe Kagome blames it on some sort of spiritual obligation, Batman says it's part of maintaining his equipment for Gotham's safety, and Superboy just stutters and says he was helping out. Then they might have to work together to deal with the consequences of being caught, like facing the wrath of a local authority or a powerful figure.
The rarity factor. Shiny Pokémon are extremely rare in the Pokémon games, so in fanfiction focusing on only catching them, it creates a sense of exclusivity. For example, in many such fanfics, the main character has to go to great lengths to find just one shiny.
Well, consider a plot where the trainer catches a Pokemon that has the ability to TF into objects or even other trainers. This could lead to some really comical and confusing situations. For example, it could transform into a Pokeball to avoid being caught by another trainer. It could also transform into a key item in the Pokemon world, like a Master Ball, and the trainer has to figure out how to get it back to its normal form without losing it forever.