One idea could be that a trainer starts with a Rotom as a starter in a region where it's not common. The Rotom could have unique abilities that help the trainer overcome challenges in the early gym battles. For example, its electric - type moves combined with its ability to possess different appliances could give it an edge in battle.
Maybe the fanfic could revolve around a Rotom starter that has a special bond with a young trainer. They go on an adventure to discover the secrets of Rotom's origin in the Pokemon world. Along the way, they encounter other trainers who are both intrigued and envious of the Rotom starter.
You could give the Rotom starter some special moves or abilities that are exclusive to it in the fanfic. Maybe it can combine its electric powers with some new type of energy it discovers during the story, like a mysterious 'ether' energy that gives it super - charged attacks.
Well, the plot could involve Ash's unique starter being from a far - off region that was thought to be extinct. This starter could hold the key to an ancient mystery in the Pokemon world. As Ash travels with it, they encounter various challenges related to protecting this starter from those who would use its uniqueness for evil purposes. The starter might also have an ability to transform into different forms depending on the situation, like a more powerful form when facing a tough opponent.
A really interesting plot might be that the Eevee is actually a reincarnation of a great Pokemon hero from the past. The trainer discovers this as they journey together and face various challenges. This knowledge makes them a target for an evil organization that wants to use the Eevee's power for their own malicious purposes. Along the way, the Eevee and the trainer meet other Pokemon and trainers who either help or hinder them in their quest to protect the Eevee's secret and fulfill its destiny.
Well, in many Pokemon fanfics about catching Rotom, the plot often involves a trainer who is on a quest to find and catch this unique Electric/Ghost - type Pokemon. Maybe they've heard rumors about Rotom's special abilities or its mischievous nature. They might have to explore an old, spooky building like an abandoned power plant where Rotom is said to lurk.
Maybe the fanfiction could focus on a trainer who gets a starter that's considered weak, like a Caterpie. But through hard work and a series of adventures, the Caterpie evolves into a Butterfree with extraordinary powers. The story could be about how they overcome the prejudice against starting with a 'weak' Pokemon and prove themselves in battles and Pokemon contests.
Well, you could have a fanfiction where the starter pokemon are in a competition not just against other pokemon but also against each other for a special prize. The trainers are caught in the middle, trying to balance their loyalty to their pokemon and the desire to win. Another interesting angle is a story where a starter pokemon is misidentified as a different type at first. Say, a Bulbasaur that looks like a Charmander because of a rare genetic mutation. This causes all sorts of confusion and challenges for the trainer. Also, a plot where the starter pokemon are reincarnations of ancient pokemon heroes and the trainer has to unlock their past memories to help them reach their full potential.
In a fanfiction like this, the plot could revolve around the fact that the egg is the key to restoring balance in the Pokemon world. The legendary starter that hatches from it is initially weak but grows rapidly under Ash's care. However, there are forces at work that want to use the starter for their own evil gains. Ash has to team up with his friends and other Pokemon to fend off these threats. The story could also explore the relationship between Ash and the legendary starter as it grows, how they learn from each other, and how their bond becomes unbreakable.
One common theme is Rotom's exploration. Since Rotom can possess different appliances, many fanfics have it exploring new places or situations by taking over different objects. For example, it might take over a refrigerator in a Pokemon center and have an adventure from there.
One interesting plot could be a young trainer who gets a starter that is considered weak, like a Caterpie, but through hard work and unique training methods, it evolves into a powerful Butterfree that surprises everyone. Another could be a trainer who has an unexpected bond with their starter right from the start, for example, a Pikachu that refuses to go into a Pokeball and they form a really close relationship like Ash and his Pikachu in the anime.
The plot could involve a young trainer starting their journey with Charizard. They might face challenges like battling against powerful gym leaders. Charizard could have unique abilities that help the trainer progress, like a special fire - based move that overcomes water - type opponents easily.