One idea could be that the Jackson twins have a secret power that they discover together. They then have to keep it hidden from the world while also trying to figure out how to use it for good.
Maybe they get involved in a time - travel adventure. They end up in different historical periods and have to find their way back home while also learning important lessons about history and themselves. For example, they could meet famous historical figures and have unique interactions with them.
Well, they could be the result of some sort of cross - over experiment gone wrong (but in a good fanfic way). Maybe they have powers from both worlds but struggle to control them at first. For example, they might accidentally cast spells while trying to use their demigod powers. And they could be the bridge between the two groups of friends. The demigods are skeptical of wizards and vice versa, but the twins help them understand each other.
One idea could be that the twins have powers from both the wizarding world and the demigod world. They can use magic spells like in Harry Potter and also have the abilities of a demigod from Percy Jackson. For example, they can control water like Percy and at the same time cast defensive spells. Another plot could be that they are sent on a mission to stop a threat that endangers both the wizarding world and the Camp Half - Blood. They have to use their combined knowledge and skills to succeed.
Perhaps they form a secret club within Hogwarts where they plan elaborate pranks on the Slytherins. This could involve using their combined knowledge of magic and mischief to outwit their rivals in really creative ways. They might also end up uncovering some dark secrets about the Slytherin common room in the process.
One idea could be that as twins, they discover a hidden power that only they can access together. Maybe it's a special jutsu passed down in their family that requires their combined efforts. For example, they might be able to open a portal to a secret dimension filled with ancient ninja knowledge and powerful artifacts.
One idea could be that Harry and the Weasley twins team up to play a huge prank on Snape. They use a combination of Fred and George's magical inventions and Harry's invisibility cloak to get into Snape's office and rearrange everything in a really chaotic way.
One idea could be Percy trying to understand the twins' pranks and finally joining in on one. Another could be the twins getting Percy to loosen up during a stressful time at Hogwarts, like exam week. Maybe they play a prank that backfires and Percy has to help them fix it without getting in trouble with the professors.
One idea could be that Harry has to team up with the Patil twins for a special magic project at Hogwarts. They discover a hidden magical artifact in the library and have to figure out how to use it without getting caught by the teachers.
One idea could be exploring their past before the events of the main story. Maybe a story about their early training or a secret mission they had to undertake together as kids.
One idea could be that the twins have unique ghost powers that are different from Danny's. For example, one twin can manipulate time in the ghost zone while the other can create portals to different dimensions. This would lead to all sorts of adventures as they try to control their powers and use them for good.
Maybe the twins are new villains in Gotham. They have unique powers that they use to challenge Batman Beyond. For example, one has the power of illusion and the other has super strength. Their combined efforts make them a tough foe for Batman to face.