Here's another idea. Oliver Potter is wrongly accused of a crime in the magical world. Marcus, who has a talent for detective - like work, decides to prove Oliver's innocence. They embark on a journey across different magical realms, encountering all sorts of strange and wonderful things. As they search for evidence, they have to rely on each other's strengths and overcome their own weaknesses. In the end, not only do they clear Oliver's name, but they also form a strong bond that changes both of their lives for the better.
Maybe Marcus is a bit of an outcast and Oliver Potter, being a popular figure, befriends him. Through their friendship, they discover a mystery about their families' pasts that they need to solve together. They go on adventures, face magical creatures and dark wizards along the way, and their friendship deepens as they uncover more about their family secrets. Along the way, they also learn more about themselves and grow as individuals.
Well, it could be that Harry Potter, while on a magical mission, somehow gets transported to Star City where Oliver Queen operates. Oliver, being the vigilant Arrow, at first mistakes Harry for a threat. But then they realize they both fight for justice in their own ways. Harry could use his magic to assist Oliver in taking down some really tough villains that the Arrow alone couldn't handle, like some dark magic - infused criminals.
You can try searching on fanfic websites like Archive of Our Own (AO3) or Fanfiction.net. Just type in the relevant tags like 'Marcus', 'Oliver Potter' and see what comes up.
Perhaps a fanfic where there's a spell gone wrong that makes Oliver Wood gain weight. Percy, with his knowledge of the wizarding rules and regulations, tries to find a way to reverse it. And Potter, well, he could be the one who encourages Wood not to give up. The story could explore how Wood copes with this new physical state, his insecurities, and how his relationship with Percy and Potter changes during this time.
In a 'bella as marcus's daughter fanfic', the plot could revolve around Bella getting involved in the vampire politics because of her relation to Marcus. The other vampire clans might see her as a threat or an asset. She would then have to navigate this dangerous world of power struggles and alliances. At the same time, she could be falling in love with a human or a vampire from a different clan, adding a romantic subplot to the story.
One possible plot could be that they face challenges from their families. Maybe Oliver's family has certain expectations for him and the baby, and Chloe's family is worried about her future. Another aspect could be how they balance their superhero/vigilante activities with preparing for the baby.
Well, the plot could involve a lot of confusion at first. Barry and Oliver would have to adjust to each other's lives. Maybe Barry in Oliver's body has to deal with the Star City politics and crime -fighting in a different way. And Oliver in Barry's body might struggle with the super - speed and the Flash's team dynamics.
One possible plot could be that Oliver, being the Quidditch enthusiast, asks Hermione for help with strategizing for an important match. Hermione uses her intelligence and knowledge of spells to come up with unique plays. Along the way, they develop a mutual respect and friendship.
One possible plot could be that Harry, after facing so much darkness in the wizarding world, is suddenly whisked away into the world of Oliver Queen. Oliver, seeing Harry's plight and his potential, decides to adopt him. Harry then has to adjust to a new life with Oliver, learning archery and self - defense skills from him. He might also bring some of his magic into Oliver's world, helping him in his fight against crime in a very unique way.
One great 'Harry Potter Marcus Flint fanfic' is 'The Redemption of Marcus Flint'. It shows Marcus in a new light, exploring his character beyond his role in the Slytherin Quidditch team. Another interesting one could be 'Marcus Flint's Secret Alliance', which delves into his possible hidden motives and relationships within Hogwarts.
In a Marcus Flint x Harry Potter fanfic, a great plot could be that Marcus Flint discovers a secret about Harry's family that could either help or harm Harry. This secret leads to a series of adventures as they try to figure out what to do with this new knowledge. It could also be a story where they are both on a quest for a rare magical item that has different significance for both Gryffindor and Slytherin, and they have to work together to find it despite their differences.