One possible plot could be that Teddy has grown up without a strong father figure and as he gets to know Harry better, he starts to see Harry as a dad. Maybe Teddy has some troubles at school or in his personal life and Harry steps in to offer guidance and support, which makes Teddy feel like he finally has a real father.
I'm not sure of a specific 'teddy calls harry dad fanfic' off the top of my head. You could try searching on fanfic platforms like Archive of Our Own. There are likely to be many fan - created stories there that might match what you're looking for.
Yes, there are likely to be such fanfics. Fanfic writers often explore unique relationships in their works, and the idea of Marcel calling Klaus 'dad' can add an interesting dynamic to a story. You can try searching on fanfic platforms like Archive of Our Own or Fanfiction.net.
Snape might be initially shocked. His face could turn pale and his eyes widen in disbelief. But then, a small glimmer of something like pride or warmth might flash across his face for a split second before he quickly composes himself and snaps at Harry to focus on the potion.
Another theme is growth. Megumi's growth as a person and as a sorcerer is often tied to his relationship with Gojo. In these fanfics, Gojo's influence helps Megumi become stronger, not just in terms of his abilities but also in his emotional maturity. For instance, Gojo might teach Megumi how to handle difficult situations, which in turn helps Megumi grow. And of course, the theme of love is there. It might not be a romantic love, but the love between a father and son. Gojo's care for Megumi and Megumi's acceptance of Gojo as a father figure is a central part of these fanfics. It gives a warm and fuzzy feeling to the readers.
The plot could involve Marcel having a crisis where he realizes that his biological family has let him down in some way, and Klaus, who has been there for him in many situations, becomes the person he looks to as a father. Maybe Marcel gets into trouble with other vampire factions, and Klaus is the one who steps in to save him, leading to this newfound father - son relationship.
In 'Harry and Teddy fanfic', the two main characters are Harry and Teddy. Harry is the one who has been through so much in the wizarding world. He has a sense of responsibility towards Teddy. Teddy is a character full of possibilities. He's the product of a tragic event (his parents' death), and Harry's presence in his life is like a guiding light. Their personalities, Harry's wisdom and Teddy's eagerness to learn, are often explored in these fanfics, which makes for very engaging stories.
One possible reason could be that in this fan fiction, Harry has developed a deep respect and a father - like bond with Snape over time. Maybe Snape has been secretly mentoring Harry in potions and has shown him kindness and understanding that Harry has never really received from his own father figure. This has led Harry to subconsciously view Snape as a father figure and the moment in potions class is just when this feeling overflows and he blurts out 'dad'.
I'm not sure about the name exactly, but there are some fanfics where Megumi calls Gojo dad in a more action - packed setting. For example, in some where they are fighting curses together. Megumi's respect for Gojo as a father - like figure is shown through their teamwork and how Gojo protects Megumi during battles.
The main characters are Harry and Teddy, but don't forget about the wizarding community around them. There could be other minor characters such as Teddy's teachers at Hogwarts when he gets older. They would play a part in Teddy's development, and Harry would interact with them to ensure Teddy has a good educational experience.