A crossover with a popular anime like Naruto could also be cool. The Smile Precure characters find themselves in the Naruto universe and have to learn ninja skills while also teaching the ninja about the power of smiles and friendship. They could participate in the Chunin Exams together or face off against a new villain created by Orochimaru who wants to steal their Precure powers.
One idea could be a crossover with another magical girl series like Sailor Moon. The Smile Precure girls could meet the Sailor Scouts and they team up to fight a common enemy that threatens both their worlds. Maybe they have to combine their powers in new and unexpected ways.
Another plot could involve a crossover with a Disney princess world. The Smile Precure girls are transported to a kingdom where they meet different Disney princesses. They work together to defeat an evil witch who has cast a spell over the kingdom. The Precure girls could use their positive energy to break the spell, and in the process, the princesses learn about the power of teamwork and modern ways of fighting evil.
Well, if it's a crossover with Pokémon, Ash Ketchum would be a great addition. He could travel with the Smile Precure girls and help them catch some Pokémon to use in their battles against the dark forces. His knowledge of Pokémon and their abilities could complement the Precure's powers.
A great plot could be that the Precures lose their memories but still feel a strong urge to fight evil. They would have to figure out who they are and what their powers are while still protecting the world. Or, you could write a fanfiction where a new villain emerges who can control the stars in a different way than the previous ones. This would force the Precures to come up with new strategies to defeat the villain.
One great Smile Precure fanfiction is 'The Adventure Beyond the Rainbow'. It takes the characters on a new journey where they discover a hidden world full of unique magical creatures. The story really captures the essence of the Smile Precure series with its positive and adventurous tone.
One idea could be creating an OC who has the power of music in the Precure world. They could use melodies to heal and fight against the villains. Another is an OC from a different dimension who stumbles into the Precure universe and has to learn their ways to help. And also, an OC that is a hybrid of a magical creature and a human in the Precure world, bringing unique powers and a fresh perspective to the story.
A good Smile Precure fanfiction often has well - developed characters. Just like in the original series, the Precure girls should have distinct personalities. For example, if one is brave and another is more gentle, these traits should be clear in the fanfiction.
A time - travel plot in a Precure All Stars fanfic could be really cool. Maybe the Precure travel back in time to the origin of their powers and have to make sure that the events that led to their powers being created happen correctly. It could involve meeting their predecessors and learning about the true nature of their powers.
One idea could be a character from the Enclave finding themselves in a situation where they have to team up with a group from the Fallout world they usually oppose. Maybe a lone Enclave soldier gets separated from his unit and is forced to rely on a group of wastelanders to survive. This could lead to a lot of character development as he sees a different side of the world outside the Enclave's ideology.
One idea could be that the Turtles from 1987 end up in the 2003 universe and have to adapt to the darker and more serious tone. They could team up with the 2003 Turtles to fight a common enemy like the Shredder. The 1987 Turtles' more light - hearted and comical ways might initially clash with the 2003 Turtles' brooding nature, but they eventually learn from each other.
One idea could be a crossover with Undertale. The characters from Glitchtale could interact with the original Undertale characters in a new and unexpected way. For example, Betty from Glitchtale could team up with Chara from Undertale for some sort of dark plan. Another plot could involve a crossover with a different game like Minecraft. The Glitchtale characters could find themselves in a blocky world, having to adapt to new rules and enemies. Maybe Sans from Glitchtale could use his powers in the Minecraft world in a really creative way.
A great plot idea would be Android 21 crossing into a world where technology is feared. She'd have to prove that not all advanced technology is bad. Also, she could cross into a world of pirates, using her skills to navigate the high seas and fight off other pirates.