Obviously, Ariel would be one of the main characters. She'd be the mermaid trying to navigate high school life. Eric could also be there as the love interest. Maybe Flounder could be her sidekick, a fish - out - of - water (literally) in the high school, always getting into comical situations. And Ursula could be the school bully or the antagonist who tries to make Ariel's life miserable.
Ariel is a must - have main character. Then there could be a new character, like a mermaid - human hybrid who helps Ariel understand both worlds better. Sebastian could be the school music teacher, always trying to get Ariel involved in the school choir. Triton could be the strict principal who has rules against mermaids revealing their true identity at school. And Scuttle could be the school librarian who gives Ariel wrong information about human things in a comical way.
Ariel would be the central figure. There could be a group of mermaid friends who attend the high school secretly. They all have different personalities. One could be really good at sports, another at academics. And then there's a human girl who becomes Ariel's best friend. She doesn't know Ariel is a mermaid at first but slowly starts to suspect and is really curious. There could also be a villainous character, a witch - like figure similar to Ursula, who wants to use Ariel's mermaid powers for her own evil plans.
Obviously, the Little Mermaid herself would be a main character. She could be joined by her friends from the sea, like a talkative seahorse or a wise old octopus who gives her advice from afar. At Ever After High, her roommates or classmates like Apple White or Raven Queen could also be important characters. They could help her adjust to school life on land.
I think Misty from the Pokemon world could be a main character in this fanfiction. Since she has a connection with water - type Pokemon, she could easily fit into the underwater world of The Little Mermaid. Along with her, a Psyduck would be there. Psyduck's clumsy yet powerful abilities could add an interesting element to the story. And of course, Ariel would be a main character. She could learn a lot from Misty about the Pokemon world and they could team up to protect both their worlds from any threats.
Well, it could be that the high school is built on an ancient underwater kingdom. Ariel, being a mermaid, senses the connection to her underwater heritage. She forms a club at school to study the history of the place. But there are other students who think she's just being weird. However, as she delves deeper, she discovers a way to bridge the gap between the mermaid world and the human high school world, all while dealing with typical high school drama like exams, prom, and friendships.
Prince Eric could be a main character. He would be important as he is Ariel's love interest. Also, King Triton, Ariel's father, could play a significant role as he would be concerned about Ursula's return and want to protect his daughter and the kingdom.
A sea - faring cat could be a new character. This cat has a special bond with the sailors on Prince Eric's ship. When Ariel comes on board, the cat is immediately suspicious of her. But as time goes on, they form an unlikely friendship, and the cat helps Ariel understand some of the human ways that the sailors have.
Maybe a lost princess from a sunken city. She has been in hiding for a long time because of some danger that destroyed her city. She meets the little mermaid and they become friends. The lost princess has unique powers related to the ancient magic of her sunken city, and she shares these powers with the little mermaid to help her in her quests.
In a 'little mermaid lemon fanfic', one of the main characters would be the little mermaid. She would be the central figure around which the story revolves. Another main character could be an old sea witch who has a connection to the lemon - related magic in the ocean. Maybe she gives the mermaid a task involving lemons in exchange for something. And a third main character could be a young human prince who loves all things lemon - flavored and is drawn to the mermaid because of her unique lemon - like charm.
For a 'Little Mermaid Naruto fanfic', Naruto and Ariel are the primary ones. However, Gaara could be an interesting addition. His past of being an outcast could parallel Ariel's feeling of not fully belonging in her own world sometimes. Then we have Ursula, the sea witch from the Little Mermaid story. In this fanfic, she could be a powerful enemy who wants to use Naruto's chakra for her own evil purposes. And Hinata could be another character, her shy nature contrasting with Ariel's more adventurous spirit as they both interact with Naruto in this unique crossover.
The main characters could be the mermaid herself, who is now a young woman with a passion for ocean conservation. And then there could be a male scientist who is researching the effects of climate change on the ocean. They meet during a research expedition and form a connection.
Obviously, Lily is one of the main characters. She's the mermaid around which the story revolves.