One common theme is power discovery. Usually, Naruto or other characters find out about new animal transformation powers they didn't know they had before. Another theme is the connection to nature. Since it involves animals, there's often a strong tie to the natural world in these fanfictions.
One great Naruto animal transformation fanfiction is 'The Fox's Pup'. It focuses on Naruto having a unique connection to his fox spirit and being able to transform in unexpected ways. It has a great plot that really dives into the lore of the Naruto world and the idea of animal transformation.
One idea could be Stuart transforming into a bird. He could use his newfound ability to fly and explore the world from above, encountering other bird species and having adventures in the sky. Another could be him turning into a fish. He'd swim in the pond or aquarium, make friends with other fish, and discover the underwater world's secrets.
In Naruto fanfiction, a lot of creative animal partners can be found. For example, there could be a magical dolphin that can swim through the air as well as water. It could be used to quickly transport the ninja across long distances. Another idea is a phoenix - like bird that can resurrect from its ashes and provide protection to its partner in the form of a fire shield. And then there's the possibility of a bear with super strength and the intelligence to strategize in battles.
One example is 'The Frog Prince'. A prince is transformed into a frog by a witch's curse. A princess kisses the frog and he turns back into a prince. It shows how love can break a transformation spell.
Animal partners can add a new dimension to the story. They can provide unique abilities that the main character might not have, like the ability to fly or sense things hidden underground. For example, if Naruto had a hawk as a partner, it could help him in scouting areas during missions.
There are several popular themes. One is the transformation for a specific purpose. For example, in some fanfictions, a human is transformed into an animal to complete a mission, like infiltrating an animal - only area to retrieve an important item. Another theme is the struggle between human and animal instincts. The transformed character has to constantly battle with their human thoughts and new animal instincts. For example, a human turned wolf might have to resist the urge to hunt during a full moon while still trying to maintain their human morality. Also, the theme of transformation as a punishment is quite common. A character does something wrong and is then turned into an animal as a form of punishment, and the story is about their redemption.
One interesting story could be about Ben transforming into a rare, mythical animal. For example, he turns into a phoenix - like alien with the ability to rise from ashes and fly at supersonic speeds. This transformation could be a result of some new alien technology he discovers. Another could be a story where he transforms into a giant sea - creature to save a sunken ship full of people. He uses his new form's strength and aquatic abilities to lift the ship to the surface.
One great example could be a story where Hermione transforms into a cat. She might use her feline form to secretly explore Hogwarts at night, sneaking into areas that are off - limits to students. In this form, she could discover hidden passages or secrets that she couldn't as a human.
One common theme is the struggle with identity. When Batman is transformed into an animal, he has to figure out how to still be the Dark Knight while dealing with new animal instincts. For example, if he becomes a wolf, he might have to control his urge to hunt. Another theme is enhanced abilities. The animal form often gives him new powers, like better senses if he's a cat or flight if he's a bird.