Maybe in this fanfiction, Harry Potter is turned into a pet dog himself by a misfired spell. As a dog, he experiences Hogwarts in a whole new way, making friends with other animals and using his dog - like senses to uncover secrets in the castle. He might even have to find a way to turn back into a human while still dealing with all the normal Hogwarts drama.
A possible plot could be that a powerful dark wizard has enchanted a Nundu to attack Hogwarts. However, one student who has a special connection with animals manages to break the spell on the Nundu and turns it into a pet. This Nundu then becomes a protector of Hogwarts, using its strength to fend off other dark creatures. Along the way, the student has to deal with the prejudice of others who fear the Nundu due to its reputation.
The plot could involve Harry, as a dog, being found as a stray in the wizarding world. He might be taken in by Hagrid, who recognizes his special magical potential. Harry could then use his dog - like instincts to discover hidden secrets in Hogwarts, like secret passages that are only accessible to small animals. He might also form an unlikely alliance with some of the other magical creatures, like the Kneazles, and together they could foil the plans of the dark wizards.
Perhaps an ancient evil that has been awakened by the presence of the pet dog in the wizarding world. This entity doesn't like the idea of a human - dog bond being so strong in a place full of magic. It starts causing chaos in Hogwarts and the surrounding areas, and Harry and his pet dog have to figure out how to stop it.
Well, it could be about a character who is forced to hide their true identity and pretends to be a pet in the wizarding world. Maybe they are on the run from some dark wizards and find a safe haven by disguising as a pet in a Hogwarts dormitory.
One possible plot could be that a new, mysterious pet appears in the pet shop in Diagon Alley. This pet has some unique magical abilities that no one has ever seen before. A young witch or wizard discovers it and tries to figure out its origin and how to take care of it. Maybe it's a key to an ancient magic mystery.
Perhaps Lemon is a dog that was once a wizard's familiar but was lost. Harry stumbles upon her and they form a bond. As Harry faces challenges in his fight against Voldemort, Lemon uses her dog - like instincts along with some latent magical abilities she has retained from her previous connection to a wizard. For example, she might be able to track Horcruxes by their unique magical scent. This would make her an invaluable asset to Harry in his quest to defeat Voldemort.
In a Harry Potter Nundu pet fanfiction, the Nundu might be a gift from a mysterious figure. The protagonist, who has always been an outcast among the wizarding community, forms an unbreakable bond with the Nundu. They embark on a journey to find a way to make the Nundu's venom, which is deadly, into a powerful potion ingredient that can save the wizarding world from a new dark threat. Along the way, they face many obstacles and make new friends who initially fear the Nundu but later come to respect it.
Well, the plot could involve the fox having some special powers that help Harry in his adventures. For example, the fox might be able to sense dark magic from afar. Harry would then have to keep the fox's existence a secret from some of the teachers who might not approve of such an unusual pet.
One idea could be that Mewtwo somehow gets transported to the Harry Potter universe. It could be mistaken for a very powerful magical creature. Harry and his friends could initially be wary of it, but then realize it has no intention of harm and they team up to fight against the dark forces in the wizarding world using Mewtwo's psychic powers.
Another plot could be that Voldemort discovers Powergirl's existence and sees her as a threat. He tries to manipulate the wizarding world against her. But Harry and his friends believe in her and together they work to expose Voldemort's lies and also learn from Powergirl about different ways of fighting evil. Powergirl could introduce new concepts of justice and heroism to the wizarding world.