Friendship is a common theme. Since they are different Pokémon types, their friendship is often explored, like how they overcome their differences. For example, Butterfree's gentle nature and Beedrill's more aggressive one can create an interesting dynamic.
One possible fanfiction could be about Ash and Serena going on an adventure specifically to find a rare pink Butterfree. Maybe they hear rumors of a special meadow where these pink Butterfree are sighted. Along the way, they face challenges like wild Pokémon and difficult terrains. Ash's determination and Serena's strategic thinking help them get closer to their goal. When they finally find the pink Butterfree, it's a magical moment, and they learn some valuable lessons about friendship and the beauty of nature.
It could be about Ash's Butterfree coming back in some way. Maybe it returns to Ash after a long time apart. It might show their reunion, and how they interact again, like Butterfree showing its affection for Ash once more.
It could be that the pink Butterfree is actually a transformed Pokémon. In the fanfiction, it could be a Pokémon that was experimented on by an evil scientist and turned into this pink Butterfree. Ash and Serena have to figure out how to turn it back to its original form. Along the way, they discover the scientist's lair and have to battle his other creations. This would be an exciting adventure full of mystery and action.
One popular Butterfree x Beedrill fanfic could be 'The Bond Beyond Types'. It focuses on how these two Pokémon, despite their different natures, form an unlikely alliance and friendship. The story is full of adventures where they help each other out in the wild.
One possible plotline could be that Ash and Serena are on a journey and Butterfree plays a crucial role in guiding them through a difficult forest. Maybe Butterfree's unique abilities, like its powder or its flight skills, help them overcome obstacles like strong winds or wild Pokémon. It could also be that Butterfree has some sort of connection to a special place that Ash and Serena are trying to reach, perhaps a place full of rare Pokémon or a beautiful meadow.
In fanfiction, shiny pokemon are often sold through underground markets or exclusive auctions. These sales are usually hush - hush due to the high value and sometimes illegal nature of trading such rare pokemon.