A snake could also be a main character. In the Naruto series, there are already snake - related characters and jutsus. A snake character could have its own motives and either be an enemy or an unexpected ally for Naruto. It could have unique abilities like camouflage or venomous attacks.
A big one could be a wolf. Wolves are often associated with strength and loyalty in many cultures, and in the Naruto universe, it could be a powerful ally for Naruto.
An eagle would be a great choice too. Eagles have excellent vision and can fly high, which could be used in many ways in the story. For example, it could be a messenger for Naruto or help him scout out enemy territory from above.
In a 'lemon animal fanfic', the main characters might be a family of lemon - colored bunnies. The mother bunny is very protective, the father bunny is brave and goes out to find food, and the baby bunnies are curious and always getting into trouble. They live in a burrow at the edge of a meadow and interact with other animals like birds and squirrels.
I think Hinata would be a main character too. If she was an animal, she might be a little rabbit, shy but with hidden strength. Her love for Naruto could be shown in different ways as an animal. And Shikamaru, as a sloth - like animal, could use his intelligence to solve problems in this new animal - filled Naruto world. Gaara, with his connection to the sand, could be a desert - dwelling animal like a scorpion, adding a new dimension to his character.
Obviously Naruto would be one of the main characters. And then there could be female Pokemon like Pikachu's female form (if we consider that in the fanfic), and female trainers such as a character inspired by Dawn from the Pokemon series. They would be the main parts of the harem, attracted to Naruto in different ways.
In this type of fanfic, Naruto is the central figure. From KHR, Gokudera would be a likely candidate for the harem. His loyalty and fiery personality would make for an exciting relationship with Naruto. Bianchi could also be part of it. Her cooking skills and her feelings for Gokudera could add an extra layer of drama. And Fon, with his calm and powerful presence, would be an important character interacting with Naruto in the harem - centered story.
Hedwig is likely to be one of the main animal characters. She was Harry's owl and had a big role in the original series, so in the fanfiction she might have even more expanded storylines. Buckbeak the hippogriff could also be a main character. He was already quite important in the books and could have new adventures in the fanfiction.
A group of monkeys might be the main protectors. Monkeys are known for their agility and intelligence. They could swing from tree to tree, launching surprise attacks on Naruto's foes. They could also use their knowledge of the forest terrain to lead Naruto to safety.
Hinata could be an idol trainee. She is shy at first but as she trains, she becomes more confident. Naruto could be her biggest supporter, and their relationship could develop further as they both pursue their dreams in the idol and ninja worlds respectively.
Felicity Smoak could be one of the main female characters. Her intelligence and tech - savvy nature could be an interesting contrast to Naruto's ninja skills. She might be intrigued by Naruto's different way of thinking and his unique abilities.
It could be Orochimaru. He's always been interested in unique powers and abilities. The idea of X - 23's mutant abilities and Naruto's jinchuriki powers would be very appealing to him. He might try to capture them both to use in his experiments to gain ultimate power.
Obviously, Naruto and Sally are the main characters. Naruto, the well - known ninja from the Hidden Leaf Village, with his orange jumpsuit and powerful jutsu. And Sally, who could be a character with her own unique traits, perhaps she's really smart or has some special ability that makes her an interesting counterpart to Naruto.