Gosling could be a time - traveling character. He could travel from the real world into the Harry Potter universe and then find a way to enter the Percy Jackson world. His knowledge from the modern world could help him solve problems in both magical realms.
One possibility is that Gosling is a long - lost relative of a powerful wizard in Harry Potter and also has a connection to a Greek god in Percy Jackson. So he has a dual heritage that gives him special abilities and a role in both storylines. For instance, he might be able to use both magic spells and demigod powers to fight against dark forces that are threatening both worlds. This would make for a very exciting fanfiction plot.
Fanfiction often takes existing characters and universes and remixes them in unexpected ways. With Gosling added to the mix of Harry Potter and Percy Jackson, we could see a story where he has unique powers or abilities that are a combination of magic and demigod skills. He might be on a quest to save both the wizarding world and the world of the Greek gods from a common threat that only his combined knowledge and skills can defeat.
Percy could fit in as a strategist. His experience in dealing with various gods and monsters gives him a unique perspective on handling threats. He might suggest different approaches that the Avengers haven't thought of before, like using the environment in a more creative way, similar to how he uses water in his battles as a demigod.
In Percy Jackson fanfiction, Goku could be a mysterious outsider who comes to help during a great war against the Titans or some other major threat. His Saiyan fighting spirit and his various energy attacks, like the Kamehameha, could be seen as a new form of magic in that world. He might not understand all the Greek mythology stuff at first, but his pure heart and desire to do good would make him a valuable ally. For example, he could team up with Percy to fight off a horde of monsters. His super speed and strength would give them an edge in battles.
He could be a mentor figure. Given his immortality and vast combat experience from the Naruto world, he could teach the demigods new ways to fight and strategize.
He could use his invisibility cloak for stealth missions with the Avengers.
Well, it could be a really interesting and terrifying addition. Maybe it could be some kind of ancient monster that was locked away long ago in the world of Percy Jackson. It could be released by some dark magic or an evil demigod. The xenomorph's ability to adapt and its deadly nature would make it a formidable foe for Percy and his friends.
The story could change in many ways. For example, Harry might start using some of the tactics that Percy uses in battles. He could also be more interested in the outdoors, like Percy, instead of just the castle grounds. And his view of magic could expand to include the more physical and elemental powers that the demigods have.
Mermaids can fit in as another species in the Percy Jackson mythology. They are part of the rich tapestry of sea - related creatures. They might have their own relationships with the sea gods. For example, they could be servants or allies of Poseidon. Their existence adds more depth to the underwater world that Percy often has to deal with.
The settings are different. Harry Potter is set mainly in the UK, at Hogwarts School of Witchcraft and Wizardry and other wizarding locations. Percy Jackson is set in modern - day USA, with a lot of action taking place at Camp Half - Blood. Also, the magic systems vary. In Harry Potter, there are spells, potions, and magic wands. In Percy Jackson, the demigods have powers related to their godly parentage like Percy can control water because his father is Poseidon. So they are clearly not related in a fanfiction way.
The concept of Animagus in an Avengers fanfiction could also be used for character development. Suppose an Avenger discovers they have the potential to be an Animagus. This would open up a whole new side of their personality. They would have to learn about magic, which is very different from their usual super - power knowledge. This could lead to interesting interactions with other characters, like Thor, who might be intrigued by this new form of power.