A great behind - the - scenes fanfiction idea could be centered around the magic that powers the Fairy Tail guild itself. How it was discovered, how it's maintained, and what role the guild members play in its upkeep. Also, the fanfiction could explore the origin of some of the unique magic items in the guild.
One idea could be exploring the daily lives of the guild members when they're not on official quests. For example, how they train in secret or their personal hobbies. Another could be about the backstories of some of the minor characters that we don't get to see much in the main series.
Perhaps a fanfiction could focus on the relationships between different guilds behind the scenes. There might be secret alliances or rivalries that are not shown in the main Fairy Tail story. It could also be about how the guild is run from a management perspective, like how they handle finances or recruitment.
One possibility is that the baby could be a key to a long - forgotten prophecy in the Fairy Tail universe. Maybe it has special powers that the villains in the fanfiction are after, and the Fairy Tail guild has to protect it.
It could be a rival guild. They might see Lucy as a threat because of her powerful celestial spirit magic. By poisoning her, they hope to weaken Fairy Tail. For example, a guild that has always been envious of Fairy Tail's reputation and power.
Natsu Dragneel could be a great character to feature. We could write about his eating habits and how he annoys the other guild members in the background. Erza Scarlet is also a good choice. We could show her behind - the - scenes preparation for battles, like polishing her armor or choosing her weapons.
One plot idea could be that Ken Kaneki somehow gets transported to the world of 'Fairy Tail'. He might initially be seen as a threat due to his ghoul nature, but as the story progresses, he could form alliances with the Fairy Tail guild members. Maybe he helps them fight against a common enemy that has some similarities to the ghoul - like threats in his own world.
One possible plot idea could be that the characters from Fairy Tail are transported to the Batman universe. Natsu, with his fire - based magic, might be seen as a new and unpredictable force in Gotham. He could team up with Batman to fight against a common enemy like the Joker, who has somehow gotten hold of some magical artifacts from Fairy Tail's world. The contrast between Batman's dark and brooding nature and Natsu's hot - headed and impulsive personality would create interesting dynamics.
Well, perhaps the OC was wrongly accused of stealing a powerful magic item from the guild. The other members turned against the OC without really listening to their side of the story. Then the OC, feeling betrayed, decides to leave Fairy Tail and seek revenge or prove their innocence on their own.
In fanfiction, their kiss could symbolize a moment of forbidden love. Zeref, with his dark past and power, and Mavis, the founder of Fairy Tail. Their kiss might be a turning point where they bridge the gap between their different natures. It could be a moment of pure emotion, defying all the odds that keep them apart in the original lore.
One idea could be Wendy going on a solo adventure to a far - off land in the Fairy Tail universe to discover a new type of magic. She could meet unique characters and face challenges that test her skills and growth as a mage.
A plot idea could be that Cana is dared to do something embarrassing in the Fairy Tail guild hall as part of a bet. She's hesitant at first but her competitive side takes over. However, things don't go as planned and she ends up in an even more embarrassing situation. Or perhaps she discovers a hidden power within herself while in an embarrassing state. She could be naked in a magical realm where she has to overcome her embarrassment to harness this new power and return to the normal world. This could lead to her becoming a stronger member of Fairy Tail.
Maybe in a fanfiction, Wendy is put under a spell that makes her think she's invisible but in reality, she's actually naked. She goes about her day in Fairy Tail, oblivious to her state, and gets into all sorts of embarrassing situations. For example, she might walk into a meeting of the guild leaders in that state. When she finally realizes, she's extremely mortified but her friends help her through it.