Perhaps a story set in a post - apocalyptic world. Matthew Daddario and Harry Shum Jr. are part of a small group of survivors. They have different skills that are crucial for the group's survival. Matthew is good at finding food and water sources, while Harry is excellent at building shelters and defenses. Over time, they face many challenges together and their relationship evolves from mere comrades to best friends who would do anything to protect each other.
A scenario could be that they are actors on the set of a big - budget movie. They play characters who are enemies in the script but in real life, they become really good friends. They start pranking each other on set, which makes the filming process more fun for everyone. Their friendship also helps them to bring out the best in their performances as they can play off each other's energy.
Romance is also quite common. Given their good looks and on - screen charisma, many fanfics explore a romantic relationship between their characters. Some fanfics also focus on the actors themselves in a 'what - if' scenario, like if they met in different circumstances outside of their shows.
You can try searching on fanfiction platforms like Archive of Our Own (AO3). There are often a lot of fan - created stories there. Just type in their names in the search bar and browse through the results.
One possible plot could be that Uncle Matthew discovers a secret portal between the Muggle and wizarding military bases. He gets caught up in a conflict where the two sides are unknowingly on the verge of war due to a misunderstanding. Harry and his friends then have to help Uncle Matthew resolve the situation before it's too late.
One idea could be a crossover where Lelouch, with his strategic mind, teams up with Harry and Percy to face a common magical - political threat. Maybe they have to infiltrate a powerful wizarding government that has been corrupted, and Lelouch uses his Geass ability to manipulate some of the key players while Harry and Percy use their magic and combat skills to fight off the guards.
One idea could be a story where Harry and Ginny are married and they take Gabrielle under their wing as a sort of apprentice in magic. Maybe Gabrielle is having trouble at Beauxbatons and they offer to help her improve her skills.
You can start by looking on fan - fiction - specific websites such as Archive of Our Own (AO3). It has a large collection of fan - created works, and there's a good chance you'll find a lot of Matthew Daddario fan fiction there.
One popular type of Matthew Daddario fan fiction might be adventure - themed ones where his character embarks on epic quests. For example, stories where he uses his charm and strength to save a fictional world.
In a more adventurous fanfiction, Harry, Fred, and George are on a quest to find a lost lemon - colored magical creature. This creature is said to be able to grant wishes. Along the way, they face many obstacles like dark magic traps and unfriendly magical beasts. They rely on their combined skills and the power of friendship to keep going on their search.
One idea could be a crossover where Fenrir from the Harry Potter universe somehow gets transported to the realm of Loki. Loki, being the trickster, might see Fenrir as a tool for his own schemes. Harry Potter, perhaps in a quest to stop some dark magic related to Fenrir, ends up following him and has to deal with Loki's antics as well.