Well, in a fanfiction about Ash catching Mew, there could be a plot where a time - traveling device gets involved. Ash accidentally travels back in time to a period when Mew was more common. He has to adapt to the different environment and rules of that time. There, he meets a young Professor Oak who is also on a quest to find Mew. Together, they embark on an adventure. Along the way, Ash shows his determination and love for Pokemon, which makes Mew interested in him. Eventually, Ash manages to catch Mew, but he also has to figure out how to get back to his own time with his new, very special Pokemon.
In some versions of the 'ash catches mew fanfic', Ash might have a special encounter with a legendary Pokémon trainer who gives him a rare item or some advice on how to catch Mew. This encounter could be the turning point in his quest. And sometimes, Mew itself may be in a situation where it's more vulnerable, which gives Ash the opportunity to attempt the catch.
In some fanfictions, Ash is on a special quest given by a legendary pokemon to catch a mythic pokemon. This quest could involve solving puzzles, traveling to different regions, and facing powerful opponents. It makes for an exciting adventure.
There are 'Ash Catches Mew' fanfictions where Ash catches Mew accidentally. He might be trying to save Mew from some other danger, like a group of poachers. In the heat of the moment, Mew decides to trust Ash and goes into his Pokéball. This unexpected turn of events then leads to a whole new adventure as Ash has to deal with the implications of having caught such a rare and powerful Pokémon.
One plot idea could be that Ash is on a journey in a mysterious forest and suddenly stumbles upon Mew. Mew, being curious about Ash's kind heart, decides to follow him on his Pokémon journey for a while. Another could be that Ash is in a dream world where he meets Mew, and Mew shows him the potential of his Pokémon in new and exciting ways. For example, Mew could transform into different Pokémon forms that Ash has always dreamed of seeing. A third idea is that Mew is injured and Ash finds it. Ash then has to protect Mew from other Pokémon or humans who might want to capture it while also trying to heal it with the help of his Pokémon friends.
One idea could be that Ash catches Zoroark in a unique way. Maybe Zoroark is disguised as a Pokémon that Ash has been longing to catch for a long time. When Ash discovers the truth, instead of being angry, he is intrigued by Zoroark's intelligence and uses his own skills and the bond with his other Pokémon to earn Zoroark's trust and catch it.
One idea could be a story where Mew and Mewtwo team up to save the Pokemon world from a new, powerful and evil artificial Pokemon created by humans. They have to overcome their differences first, as Mewtwo still has some resentment towards humans and Mew is more open - minded.
Perhaps Mew and Mewtwo are in a fight against an evil force that threatens the Pokémon world. Ash arrives at the scene and manages to communicate with them. He offers his help and through their combined efforts, they defeat the evil. As a result, Mew and Mewtwo see Ash as a true hero and allow him to catch them, leading to a new chapter in Ash's Pokémon journey.
One idea could be that Mew and Celebi team up to save a dying forest. Since Celebi has a strong connection to nature and Mew is a very powerful and curious Pokemon, they could use their unique abilities to heal the forest. Maybe there's a dark force polluting the forest, and they have to find the source and stop it.
The unique personalities of the characters make it interesting. Ash is always eager to learn and grow, Mew is full of mystery and playfulness, and Mewtwo has its complex backstory and powerful abilities. When combined in a fanfiction, their interactions can be really engaging.
Perhaps in the fanfiction, Cynthia could be mentoring Ash in some advanced Pokemon battling techniques. Ash, being eager to learn, follows her guidance and in the process, they develop a deeper bond. This could lead to them exploring new regions together in search of rare Pokemon for training.