You could also write a fanfiction where the fairies have to deal with a new villain that is immune to their usual magic tricks. This would force them to come up with creative new ways to protect Timmy. They might have to team up with other magical creatures they usually don't interact with, and it could be a great adventure - filled story.
One idea could be exploring what would happen if Timmy's fairies got their powers mixed up. For example, Cosmo could accidentally get Wanda's more organized and rule - following magic abilities, leading to some really funny situations where he tries to be super strict with Timmy's wishes in an un - Cosmo - like way.
Well, you could write a 'fairly oddparents fanfiction' where the roles are reversed. For instance, the fairies become the ones in need of help and Timmy has to use his non - magical human skills to save them. Or perhaps a story set in the future where Timmy has grown up and is now a fairy godparent himself, and he has to guide a new, young kid. You could also do a crossover with another kids' show universe, like having some characters from that universe end up in Dimmsdale and interact with the 'fairly oddparents' characters.
Another interesting concept is to write a fanfiction where a new character enters Dimmsdale. This character has a strange connection to the magic of the fairies, and it causes all sorts of chaos and new adventures for Timmy and his friends. Maybe this new character is from a parallel dimension where the rules of magic are different.
Maybe an OC who comes from a long - lost family of fairies. This OC could be on a quest to discover their family's past and their rightful place in the fairy world. They could encounter various characters from the Fairly OddParents universe along the way and have all sorts of adventures with them.
One idea could be a crossover with 'The Powerpuff Girls'. The Fairly OddParents' magic could interact with the superpowers of the Powerpuff Girls in really fun ways. For example, Timmy could wish for super strength like Buttercup, but with a magical twist. Maybe his strength would be based on how many good deeds he's done recently.
One idea could be a fanfiction where Timmy's new baby sibling gets fairy godparents too. Maybe they have really unique and wacky wishes that cause all sorts of chaos in Dimmsdale. Another idea is a story where a baby from another dimension ends up in Dimmsdale and the Fairly OddParents have to figure out how to send it back while also taking care of it.
One idea could be that Jess from 'New Girl' somehow discovers she has fairy godparents like in 'Fairly OddParents'. Maybe she wishes for a perfect roommate and Timmy's fairies, Cosmo and Wanda, get sent to her by mistake. Then all kinds of wacky adventures start as they try to figure out how to get back to Timmy while also helping Jess with her life in the loft.
Character - development fanfiction is also great. It could explore how a character like Cosmo grows and changes over time. Maybe he has to face a personal challenge that forces him to become more responsible. This type of fanfiction can add depth to the characters we already love from the show.
One interesting storyline could be Timmy Turner using his fairy godparents' wishes in creative ways to solve problems in the human and fairy world simultaneously. For example, he might wish for a device that can translate all languages so that he can communicate with fairies from different regions and help them resolve misunderstandings. Another could be a story where Vicky, his babysitter, gets a taste of her own medicine through a wish gone wrong and has to experience what it's like to be in Timmy's shoes for a day.
One common theme is the Tooth Fairy's relationship with the other magical characters in The Fairly OddParents universe. For example, how she interacts with Cosmo and Wanda.
You could do a time - travel fanfiction. Have a character go back in time to when the Fairy Tail guild was first founded and see how they interact with the founders. Or, write a story where the characters swap powers. So, Erza would have Lucy's celestial magic and Lucy would have to use Erza's requip magic. This would lead to a lot of comical and also challenging situations for them. Also, you could write a fanfic about the guild taking on a mission in a completely new and strange land, filled with magic they've never seen before.