One idea could be to explore what would happen if Sora and his friends got trapped in Ariel's underwater world during a Heartless attack. They'd have to team up with Ariel and her friends to fight off the Heartless while also dealing with Ursula's schemes in a new way.
Ursula is an obvious choice as she is the main villain in the original Little Mermaid story. In a Kingdom Hearts fanfiction, she could be even more powerful, perhaps having made a deal with the Heartless or some other dark force to gain more control over the underwater world and other worlds connected to it.
One possible plot could be that Sora and his friends land in the underwater world of The Little Mermaid. Ariel could be in trouble, perhaps captured by the Heartless. Sora, with his Keyblade, would fight to free her. Donald and Goofy could help by using their magic and strength respectively. They would then have to find a way to restore the underwater kingdom's heart which has been affected by the Heartless presence.
Sora would likely be very protective of Ariel. He would see her as someone in need of help, just like he does with many characters in different worlds. Ariel, on the other hand, would be fascinated by Sora's world and his Keyblade. She might ask him a lot of questions. Donald could get frustrated with Ariel's overly curious nature at times, while Goofy would just be friendly and go along with whatever is happening.
I've come across a fanfiction titled 'Chicken Little's Heart of Courage in Kingdom Hearts'. This fanfic delves deep into Chicken Little's character development. It shows how he overcomes his fears in the strange and often dangerous world of Kingdom Hearts. The author has created some really cool new scenarios and battles for Chicken Little. It also has some great dialogue that makes you feel like you're really there in the story, watching it all unfold.
The unique aspect of Kingdom Hearts Chicken Little fanfiction is the blend of two very different universes. Kingdom Hearts has its own complex lore and a large cast of characters, and Chicken Little brings his own charm and simplicity. When combined, it creates stories that can be both humorous and full of heart. For example, seeing how Chicken Little reacts to the Heartless or how he interacts with keyblade wielders like Sora is really interesting.
The themes of friendship and believing in oneself from 'Little Witch Academia' could be further explored in the context of Kingdom Hearts. How the characters face the darkness and find the light within themselves while also dealing with the Heartless could make for a very engaging fanfic. The relationships between the 'Little Witch Academia' characters and the Kingdom Hearts regulars like Donald and Goofy could also be developed in unique ways.
Well, it depends on how you look at it. Technically, in official Kingdom Hearts content, Sora is a key character. But in the realm of fanfiction, many writers take the essence of Sora and create their own unique stories that are not part of the official canon but are still inspired by the Kingdom Hearts universe. So, in that sense, he can be considered as a major element in Kingdom Hearts fanfiction.
Another storyline might involve a character from Kingdom Hearts getting lost in the 'Little Witch Academia' world. For instance, Riku could end up there and have to work with Akko to find a way back. Along the way, they could exchange knowledge about their different worlds and powers. This could lead to some interesting battles against local villains in the 'Little Witch Academia' world who are interested in Riku's power.
Ursula as a mermaid in fanfiction might also explore her backstory more deeply. She could have been a mermaid princess in a far - off part of the ocean. But due to a power struggle or a curse, she lost her status and became the villain we know. This could add a lot of depth to her character and make the fanfiction really engaging.