Hoopa's powers of creating portals can be used to transport Ash and his friends to different eras in Pokémon history. They could meet ancient Pokémon trainers or see how Pokémon evolved over time. Another way is to use Hoopa's power to summon different types of Pokémon from all over the world for a big Pokémon gathering or a battle royale. Also, Hoopa could use its powers to create illusions, like making a fake treasure that villains are after, leading them on a wild goose chase while Ash and his friends work on a real problem.
There might be a 'pokedex horror story' where the Pokedex starts to give out strange and menacing messages about an upcoming disaster related to Pokémon. It warns the trainer but no one else believes it, creating a spooky situation. The trainer has to figure out if it's a real threat or just a malfunction while being constantly on edge.
The 'pokedex horror story' might be about glitches in the Pokedex system that lead to terrifying situations. For example, it could show Pokémon that are not supposed to exist or have distorted appearances. It could also be about a Pokedex that somehow predicts doom or danger related to certain Pokémon.
Some plot ideas might include Ash and Hoopa teaming up to rescue a group of Pokémon that have been captured by an evil organization. Hoopa could use its portals to get into the enemy's lair. Another plot could be that Hoopa gets sick, and Ash has to find a way to heal it. He travels far and wide, meeting different Pokémon and people who might have the cure. And there could be a story where Hoopa reveals a hidden world to Ash, a world full of ancient Pokémon and secrets. Ash then has to explore this world with Hoopa and make sure these secrets don't fall into the wrong hands.
One of the popular characters might be the main Pokedex holder, who is often depicted as brave and curious. Another could be a rival Pokedex holder, adding some competition and drama to the story. Also, some of the Gym Leaders or Elite Four members from the original Pokemon series might make appearances and be popular in these fanfics as well.
Misty is also a character that shows up a lot. Her knowledge of water - type Pokemon can be combined with her role as a Pokedex holder. Fanfictions might explore her adventures in different regions, her encounters with new Pokemon, and how she uses the Pokedex to learn more about them.
There could be stories about the adventures of different Pokedex holders. For example, they might encounter rare Pokemon, explore uncharted regions, or face off against powerful villains. The Pokedex holders could also have unique relationships with their Pokemon that are explored in these fanfics.
One interesting story could be about a Pokedex holder's journey to discover a rare and powerful Pokemon. They might face various challenges and meet unique characters along the way.