Who could be the antagonist in a 'Harry Potter Tonks Potion Mishap' fanfiction?

One possible plot could be that Tonks accidentally creates a potion that makes her swap appearances with Harry. This would lead to a series of comical and confusing situations. For example, Tonks (in Harry's body) has to deal with Harry's friends not realizing it's her, and she has to figure out how to reverse the effect while also not getting Harry into trouble at Hogwarts. Meanwhile, Harry (in Tonks' body) has to navigate the world of the Order of the Phoenix and deal with Tonks' responsibilities.

In a Harry Potter polyjuice potion mishap fanfiction, the person who drinks the potion wrongly might start to exhibit the wrong personality traits. Let's say they were trying to transform into Hermione but due to the mishap, they start acting like Draco Malfoy instead. This would cause chaos as they would be doing things completely out of character for the person they were supposed to be imitating. They might start bullying other students or being mean to their friends, creating a lot of drama and confusion in the wizarding world.

Ron could be the main character in a Harry Potter polyjuice potion mishap fanfiction. Ron is known for his sometimes hasty decisions. He might be so eager to prove himself or get involved in some secret mission that he doesn't follow the potion - making instructions properly. This could lead to a mishap where he transforms into an unexpected person, and then has to navigate through the wizarding world in this new form, trying to hide his identity from his friends and family while also trying to reverse the effects of the potion.

Another possible antagonist could be the Ministry of Magic. If they suspect Harry of something and force Tonks to spy on him or cut ties with him, it would break Harry's heart. The Ministry's strict rules and paranoia could be the driving force behind Tonks' actions that lead to Harry's heartbreak.

One possible scenario in this fanfic could be that Harry and Blaise are working on a difficult potion in Potions class. Maybe they accidentally add the wrong ingredient due to a misunderstanding or a distraction. This could lead to a potion that has unexpected effects, like making them swap voices or even temporarily change their physical appearances.

There are also some original characters created in fanfiction who are potion geniuses. These characters can bring new storylines and perspectives to the world of Harry Potter potions. They might have unique ways of brewing potions or discover new potion recipes that change the magical world.

Hermione could be the main character. Given her inquisitive nature and love for knowledge, she might be involved in an experiment that causes a DNA mishap. For example, she could be researching a new spell in the library and accidentally triggers a reaction that messes with her DNA. This would be a huge challenge for her as she's always been in control of her studies and actions, and now she has to deal with unexpected changes to her body and abilities.

Tonks might be hugging Remus Lupin. Since they have a romantic relationship in the Harry Potter series, a hug could be a way to show their affection, and the 'mine' could be part of an adventure they share together.

Perhaps a long - lost relative of the Potter family who feels they were unjustly excluded from inheriting the manor. This relative could be jealous of Harry's status and the wealth associated with the manor. They might use dark magic to try and claim what they think is rightfully theirs, leading to a battle of magic and loyalty within the Potter family and among Harry's friends.

It could be some dark wizards who want to use the centaur's parts for potions. They might be following some ancient, dark magic recipe that requires centaur hair or hooves. So they hunt down the centaur, but Harry gets in their way.