One idea could be a story where Mash teams up with an unlikely ally from a rival school. They start off not getting along but through various challenges, they learn to work together and combine their unique skills.
A fanfiction could explore what would happen if Mash suddenly lost his magic but had to rely solely on his muscles to get through a series of magical trials. This would force him to find new ways to overcome obstacles and show his true strength.
The Mashle: Magic and Muscles manga is finished. It reached its conclusion, leaving fans with a complete narrative and memorable moments.
Another option could be a student from a different magic school who is jealous of Mash's popularity and unique abilities. This student could use dark magic to try and bring Mash down.
Some interesting Magic Tree House fanfiction ideas might include a scenario where Jack and Annie are transported to a world that is on the brink of a war between different magical creatures. They have to use their wits and the knowledge they've gained from their previous adventures to broker peace. Another idea could be that they find themselves in a world where time moves differently, and they have to adapt quickly to avoid getting trapped there forever. You could also write a fanfiction where they visit a world filled with lost ancient civilizations and have to unlock the secrets of those civilizations to continue their journey.
One idea could be a prequel story focusing on how Mike got into the stripping business. Maybe he had a bet with a friend or was in a tough financial situation and saw it as a quick way to make money.
One idea could be a crossover with a superhero universe. Picture Magic Mike and his crew performing at a charity event in Gotham City, and they end up getting involved in a plot by one of the villains. Another could be a crossover with a fantasy world, like they are transported to a magical realm where their dancing skills are seen as a form of magic. Or perhaps a crossover with a classic movie world, like they perform in the 1920s Chicago from a gangster movie.
Another interesting plot is a crossover where the Magic The Gathering planeswalkers end up in the Naruto world. They could interact with the ninja clans and get involved in the power struggles. For instance, a planeswalker might team up with Naruto to fight against the Akatsuki, bringing their unique Magic The Gathering powers to the fight. This could lead to all sorts of new strategies and battles.
One interesting idea could be the creation of new and unique magic circuits that combine different spells or magical elements. For example, a circuit that mixes a protection spell with a levitation charm in a novel way. Another idea might be the use of magic circuits to enhance magical creatures' abilities, like creating a circuit for a hippogriff to fly faster. Also, some fanfictions might explore how magic circuits can be used to solve complex magical problems within Hogwarts, such as fixing the broken staircases more efficiently.
One idea could be that Naruto discovers a set of ancient cards with hidden jutsu. He has to learn how to use the card magic to defeat a new, powerful enemy threatening the Hidden Leaf. Another could be that the cards are used in a tournament among the ninja villages, and Naruto represents Konoha in the card magic battles.
Another interesting plot could be a young wizard who is initially not good at traditional magic but has a natural talent for music magic. They struggle to be accepted in the Fairy Tail guild at first because their magic is so different. However, as they grow and develop their skills, they end up saving the guild from a powerful enemy using their music magic in a very unexpected way.
One interesting idea could be a new spell using lightning magic that only a chosen few can master. It might be a spell that can either protect Hogwarts in a more powerful way than existing spells or be used to track dark wizards by following the electrical impulses in their magic.