Imagine if the gods in the Percy Jackson universe decide to test the mortals in the Kickin It world. They send Percy as a sort of envoy. Percy arrives at the dojo and challenges the students there to a series of tests. At first, the Kickin It gang is angry and confused. But as they engage in these tests, they start to learn about their own hidden potential. Meanwhile, a dark force from the underworld notices this interaction and tries to disrupt it. Percy and the Kickin It gang then have to work together to defeat this dark force. Along the way, they exchange their skills and knowledge, with Percy teaching them about Greek mythology and the Kickin It gang teaching him martial arts moves.
One possible fanfic could start with Percy Jackson, on a break from his demigod adventures, stumbling upon the dojo from Kickin It. He's intrigued by the martial arts skills he sees. He decides to join in for a while, hiding his true identity. But soon, his demigod reflexes start to show and the kids at the dojo are both amazed and a bit suspicious. As he trains with them, he also starts to notice some strange magical auras around the place, which could be related to some minor godly influence.
One possible plot could be that Percy and his demigod friends are somehow transported to the Halo universe. They could team up with the Spartans to fight a common enemy, like a new kind of powerful monster that has emerged in the Halo world due to some strange rift between the two universes. Percy could use his water powers in unique ways, for example, to short - circuit some of the Covenant technology which might be vulnerable to water in this crossover scenario.
One idea could be that the demigods from Percy Jackson's world end up in Forks for some reason. Maybe they are on a quest that leads them there. And they cross paths with the vampires and werewolves from Twilight. For example, Percy could use his water powers to fend off some danger that the Twilight characters are facing, like a wildfire started by a vampire's power going out of control. This would create an interesting dynamic as the two different mythologies collide.
One idea could be that the demigods from Percy Jackson's world accidentally stumble into the realm of the Kane Chronicles. Maybe Percy, Annabeth and some of their friends are on a quest near a portal that leads to the Egyptian magical world. Once there, they meet Carter and Sadie Kane. They soon realize that there's a common enemy that is affecting both their worlds, like an ancient evil that was sealed away long ago but is now starting to break free. They have to combine their powers, the Greek magic and the Egyptian magic, to fight it off. For example, Percy's control over water could be used in creative ways in the Egyptian deserts, and the Kane's magic could help the demigods in understanding some new types of magical threats.
A possible plot is that Voldemort discovers the existence of the demigods and tries to use their powers for his own evil purposes. He sends his Death Eaters to capture some demigods. Percy and his friends manage to escape and seek refuge at Hogwarts. At Hogwarts, they learn about magic in a whole new way while also teaching the wizards and witches about their own powers. The two groups then have to combine their skills, like the demigods' combat abilities and the wizards' spell - casting, to fight against Voldemort and his new - found allies from the world of Greek mythology.
A cool plot might involve a character from the Percy Jackson series getting lost in the Kane world. For example, Percy could end up in the Kane world and not understand how their magic works. The Kane siblings would have to help him while also dealing with their own problems, like the threat of some dark magician. At the same time, Percy's friends from his world are trying to find a way to bring him back, leading to an interesting crossover of events and character interactions.
One plot idea could be that Percy Jackson discovers a magical artifact that somehow links his world to the Marvel Universe. Thor senses the power of this artifact and comes to investigate, leading to a meeting with Percy. Meanwhile, the Avengers also get wind of it and think it could be a threat. So, they all end up in a big showdown where they have to figure out if they're on the same side or not.
One idea could be that the wizarding world discovers the existence of demigods. Harry and his friends team up with Percy and his crew to fight a common enemy that threatens both their worlds, like an ancient, powerful dark force that feeds on magic and the power of the gods. For example, a new kind of dark wizard who has made a pact with a minor, evil god.
Maybe there could be a new threat that can only be defeated by combining the magic of the Greek demigods and the Egyptian magicians. For example, a powerful monster that is immune to the weapons of one group but vulnerable to the powers of the other. Percy and his friends would have to team up with Carter, Sadie and their crew to take it down. They would need to learn about each other's worlds and powers along the way, which could lead to some interesting character interactions.
Well, one possible plot could be that the gods in the Percy Jackson universe notice some strange energy disruptions caused by the Infinity Stones in the Avengers' world. Percy and his friends are sent to investigate. They meet the Avengers and at first there are misunderstandings, like the Avengers thinking Percy's powers are from some new form of alien technology. But then they realize they need to work together to stop a common enemy, perhaps a new powerful being that is drawn to the combined power of the demigods and the Infinity Stones.