A wise old sea turtle could be a new character. He could be the one who gives the mermaid advice about the human world and warns her of the potential dangers.
There could be a human girl who befriends the mermaid when she's on land. This girl could be different from the prince, more curious about the mermaid's world and helps her hide her true identity from others. For instance, she might teach the mermaid how to dress like a human and blend in better.
A mysterious sea witch who is neither completely good nor completely bad. She might offer the mermaid different kinds of magic in exchange for favors. This character could add an element of unpredictability to the story and force the mermaid to make difficult choices.
A merman from a far - off part of the ocean. He could have unique powers, like the ability to control the tides. He might befriend Ariel and join her on her adventures, or he could be a rival for her affections.
A sea turtle that has seen many centuries pass could befriend Melody. The sea turtle could tell her stories about the ancient times of the ocean, give her advice on how to handle difficult situations, and guide her through some of the more dangerous areas of the ocean that are filled with magic and mystery.
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.
A wise old owl could be a new character. This owl could be the one who actually has knowledge about the real threats (or lack thereof) in their world. Maybe he tries to guide Chicken Little and the other animals. Another potential character could be a mischievous squirrel. The squirrel could be constantly causing small troubles that make Chicken Little think the sky is falling all over again. For example, it could knock down acorns that make loud noises.
There could be a rival mermaid who is jealous of the main mermaid's transformation. This rival might try to sabotage the transformation or create trouble for the mermaid in her new human life. She could be envious because she always wanted to experience the human world but was too afraid to take the risk of transformation.
A merman who was once in love with Ariel but turned bitter when she chose Eric. He could team up with some sea monsters and try to take Ariel back to the sea against her will, believing that she made the wrong choice in leaving the ocean for a human.
A group of mermaids from a far - off and isolated reef who are jealous of Ariel's family and their influence. They could plot to make Melody look bad in front of the underwater kingdom.
A new friend for the little sister from outside the Lab Rats' world. This character could introduce her to normal teenage life things like school dances and homework, which would be a contrast to her life as part of the Lab Rats' family. It could also create some internal conflict as she tries to balance both aspects of her life.
Well, of course, there's the little vampire himself. He could have a best friend who is a human, a brave kid who is not afraid of the vampire's nature. There might also be an old vampire mentor who teaches the little one about vampire traditions and how to control his thirst.