A crossover with 'Star Trek' would be cool. The Magic School Bus could transform into a spaceship and travel to different planets. The students would meet alien species and learn about their cultures and technologies. They could use the scientific concepts they've learned on the Magic School Bus to communicate with the aliens.
One idea could be a crossover with 'Harry Potter'. The Magic School Bus could take the students to Hogwarts. They could learn about magic from the Hogwarts professors and compare it with their own scientific knowledge. Maybe they'd help Hermione solve a complex potion problem using scientific methods.
One idea could be an OC who has a special power related to time. They could accidentally send the Magic School Bus to different eras in history, creating all sorts of chaos and educational adventures. For example, they might end up in the Ice Age and have to figure out how to survive and learn about the animals and climate of that time.
One idea could be a crossover with a superhero universe. Picture Magic Mike and his crew performing at a charity event in Gotham City, and they end up getting involved in a plot by one of the villains. Another could be a crossover with a fantasy world, like they are transported to a magical realm where their dancing skills are seen as a form of magic. Or perhaps a crossover with a classic movie world, like they perform in the 1920s Chicago from a gangster movie.
If it was a crossover with 'Percy Jackson', Percy could be a main character along with the Magic School Bus gang. Percy could show them around Camp Half - Blood and they could learn about Greek mythology. Meanwhile, the Magic School Bus students could teach Percy about science and how it might relate to the magic in his world.
One idea could be Naruto characters attending a modern-day high school. For example, Naruto could be the class clown who always gets into trouble but has a heart of gold. Sasuke might be the mysterious loner that all the girls are curious about. Another idea is a school tournament where Naruto and his friends use their ninja skills in a non - lethal way, like a sports - like competition within the school grounds.
One idea could be to cross it with a superhero universe. Imagine the characters from 'the god of high school' getting superpowers and teaming up with well - known superheroes to fight a common enemy. Another idea is to crossover with a fantasy world like Middle - earth. The combat - loving characters would fit right in among the elves, dwarves and hobbits. A third idea could be a crossover with a post - apocalyptic setting, where their martial arts skills are put to the test in a world full of danger and chaos.
You could do a crossover with 'Sword Art Online'. The virtual reality aspect of SAO could be combined with the supernatural elements of High School DxD. For example, the characters could be trapped in a virtual world that has elements of both worlds, and they have to fight their way out. Issei might have to use his skills in a new digital environment while also dealing with SAO - like challenges.
Perhaps the Magic Knights are called to a different realm because there are dark forces there that are somehow related to the enemies they fought in their own world. They meet characters from that world who have unique powers. The Magic Knights then have to combine their powers with these new characters to stop the spread of the darkness. They might face challenges like cultural differences and different ways of using magic.
Another idea could be Harry learning magic from a time - traveling wizard from a far - off future. This would introduce futuristic magical concepts and technologies that he would have to adapt to. It could also lead to him having to use his traditional Hogwarts magic in new and unexpected ways to keep up with the advanced magic he's learning.
One idea could be that the Magic God decides to test Harry Potter by sending him on a special quest that involves both the wizarding world and the realm of the Magic God. Harry might have to use his unique skills as a wizard and also learn new powers bestowed by the Magic God.
One idea could be exploring the backstory of Tatsuya more in - depth. Maybe his early training days and how he developed his unique abilities.