A possible plot could be that Ash is given a special Porygon by Professor Oak that has a connection to Dexter. The Porygon has a hidden power that only Ash can unlock. As they explore different regions, Ash and Porygon train together, with Dexter providing useful information. However, a mysterious organization wants to capture Porygon for its power. Ash has to protect Porygon and figure out how to fully utilize its power to defeat the organization.
Well, some Pokemon - related forums might also be a good place to look for this fanfiction. There are often sections dedicated to sharing and discussing different fan - created stories. For example, the Serebii.net forums could potentially have what you're seeking. You'd need to register and then use their search function to find any stories involving Ash, Dexter, and Porygon.
A plot where Dexter's technology malfunctions and sends Ash into an alternate Pokemon universe. In this universe, the roles of Pokemon and trainers are reversed, and Ash has to figure out how to get back while also dealing with this strange new world. This could involve lots of interesting interactions and battles. For example, he might have to convince the Pokemon to help him instead of commanding them like he's used to. It would also be a great opportunity to explore different character relationships and how they adapt to this new situation.
One possible plot could be a race between Porygon and Pikachu. Since Porygon can move quickly in digital spaces and Pikachu is super fast, they could compete in a unique race. Maybe the prize is a rare Pokemon item.
One possible plot could be that Ash and Jessie, instead of being rivals, team up to face a new and powerful threat in the Pokemon world. Maybe a new villain emerges who has the ability to control Legendary Pokemon and is causing chaos. Ash, with his extensive knowledge of Pokemon training, and Jessie, with her cunning and resourcefulness, combine their skills to take on this foe. They start to respect each other's abilities more as they journey together, and along the way, they also discover new Pokemon species and hidden secrets about the Pokemon world.
Well, perhaps in the fanfiction, they discover Serena's pregnancy during an important Pokemon battle tournament. This news spreads among their friends and fellow trainers. Some are overjoyed and offer support, while others are a bit skeptical about how they'll manage both family and their Pokemon - related duties. They then have to figure out how to balance their passion for Pokemon with the new responsibilities of parenthood.
One possible plot could be that Ash travels to Queen Ilene's kingdom. There, he discovers a new type of Pokemon that is native only to that area. Queen Ilene asks for Ash's help in protecting these Pokemon from a group of poachers. Ash, with his Pikachu and other Pokemon friends, devises a plan to stop the poachers and in the process, he learns about the unique culture and history of the kingdom.
It could be that Mew has some sort of special power or knowledge that certain groups in the Pokémon world are after. They see Ash as an obstacle to getting what they want from Mew. So, they scheme to make everyone think Ash is untrustworthy. His friends, not knowing the truth, end up betraying him. Ash then has to fight against all odds to protect Mew and regain the trust of his friends.
In this fanfiction, if Ash turns into a pokemon, perhaps he becomes a Charmander. He could struggle with being in a different form. He might have to adapt to the life of a fire - type pokemon, facing challenges like being weak against water - type attacks and trying to find a way to change back while still having adventures with his friends, who now have to protect him in a different way.
There might be a fanfiction where Ash discovers a unique Pyrigon in a hidden forest area. With Dexter's help in researching its abilities, they form a special bond with the Pyrigon and embark on a journey to help it reach its full potential. This journey involves facing off against other trainers and wild Pokemon.
One possible plot twist could be that the person Ash thought was his friend in Orre turns out to be working for an evil organization. Another could be that Ash's Pokemon are somehow brainwashed against him. Maybe the betrayal leads to Ash losing his ability to communicate with his Pokemon for a while.