A really interesting plot could be where in the 'make a wish' world, there is a glitch that causes all the wishes to go wrong. The main characters have to figure out how to fix the glitch before the entire world of wishes collapses. It could involve them going on adventures to different wish - granting places, meeting strange creatures that are a result of the wrong wishes, and using their wits and the power of friendship to solve the problem.
A 'make a wish' Harry Potter fanfiction could revolve around a spell gone wrong. Maybe Hermione was experimenting with a new charm in the library and it backfires, creating a wish - granting situation. Harry wishes for the safety of all his friends during the final battle, which then sets in motion a series of events where they all gain special powers or protections that they need to figure out how to use effectively.
Well, in this fanfic, perhaps Harry makes a wish for a world where magic and Muggle technology can co - exist peacefully. This would lead to some really cool crossovers, like wizards using smartphones to communicate. Or he could wish for a more inclusive Hogwarts, where all magical creatures are treated equally and can study there.
One idea could be that a character wishes upon a star to bring back a lost loved one. But when the loved one returns, they are not quite the same as before, leading to a journey of rediscovery. Another plot could involve a character wishing for a special power, like the ability to fly. However, they soon realize that with great power comes great responsibility and have to deal with the consequences of their wish.
One idea could be that a young fan makes a wish to meet Batman through a Make - a - Wish - type foundation. Batman then takes the kid on a tour of the Batcave, showing him all the cool gadgets and explaining how he uses them to fight crime. It would be a heartwarming story of a hero making a child's dream come true.
One idea could be exploring Puss's past adventures before the events of the movie in more detail. For example, his encounters with other magical creatures and how those experiences shaped him into the cat he is in the movie.
One idea could be a character from the 'Make It or Break It' universe having to overcome a serious injury and still compete. Another could be a romantic relationship developing between two characters who are rivals in the gymnastics world. Maybe a character gets an unexpected opportunity to train with a famous coach and has to decide if they should take it or not.
One idea could be Percy wishing for a day without any monsters chasing him. He could finally relax and enjoy a normal day at Camp Half - Blood, maybe have a picnic by the lake. Another idea is that he wishes to bring back a fallen demigod friend. This would lead to a lot of emotional reunions and also some complications as the friend might not be the same after coming back from the dead.
One idea could be a modern-day take where a young girl in a big city wishes upon a star and suddenly finds herself in a magical realm that exists parallel to her own world. There, she meets characters from her favorite stories who are also trying to make their own wishes come true. Another could be a story about a group of friends who all wish upon the same star at the same time and their wishes get intertwined in unexpected ways, leading to a series of adventures as they try to figure out how to handle the consequences of their combined wishes.
One interesting wish for Percy could be to have a day where all the Greek gods and goddesses get along peacefully. This would be a huge change from the constant bickering and power struggles they usually have. It would also mean a more stable world for demigods like Percy. He wouldn't have to worry about being caught in the middle of their feuds or being sent on dangerous quests because of their disputes.
One idea could be that they are thrown into an alternate dimension where the normal rules of their relationship don't apply. In this dimension, they gradually discover new feelings for each other as they face various challenges together.