Naruto could be included. Since he has a connection to the tailed beasts in his own universe, it would be interesting to see how he interacts with the three - tailed beast in a different setting. Maybe he could help the three - tailed beast understand the new world it has crossed over into.
In a more magical - themed crossover, characters like Harry Potter could be involved. He could use his magic to communicate with the three - tailed beast in ways that others couldn't. Also, Hermione with her vast knowledge could help figure out a way to send the three - tailed beast back to its original world if that was the goal of the story. There are also characters like Frodo from The Lord of the Rings. His journey - like nature could parallel the three - tailed beast's own journey in the new world it has entered.
Characters from the 'Smallville' universe could be great. Clark Kent, for instance. Imagine The Flash and Clark Kent working together. Clark's super strength, invulnerability, and other powers combined with The Flash's speed would be an unbeatable combination. They could face off against a powerful Kryptonian villain who has come to Earth to cause chaos.
Oliver Queen from Arrow would be a great addition. His archery skills and combat experience could complement The Flash's super - speed. Also, Kara Danvers from Supergirl could be included. Her super - strength and flight would add a new dimension to the crossover. And of course, the Legends of Tomorrow crew like Sara Lance, who has her own set of combat and leadership skills.
If it's a crossover with the Final Fantasy series, characters like Cloud Strife could be included. Cloud's brooding nature and combat skills would contrast with Professor Layton's calm and cerebral approach. Tifa Lockhart could also be part of it, providing her own brand of strength and determination.
How about including characters from Sailor Moon? It would be really interesting to see the Gokaigers interact with the Sailor Scouts. Maybe they could learn some new strategies from the Scouts' magic-based attacks.
Shadow the Hedgehog would be an interesting addition to a crossover. In a crossover with the DC Universe, he could be compared to Batman. Shadow's brooding nature and combat skills could make him a formidable ally against villains like the Joker and Dr. Eggman. He could use his Chaos Control ability to quickly move around Gotham City or Sonic's zones, just like how Batman uses his gadgets to traverse the city.
Well, they could cross over with characters from other Nickelodeon shows like the Winx Club. The fairies from Winx Club could interact with Shimmer and Shine, sharing different kinds of magic. They could have a magical battle together against a common enemy.
If it's a crossover with the Power Rangers, the Rangers themselves would be obvious choices. They could combine their Zords and powers to take on King Ghidorah. Each Ranger could use their unique skills and weapons to try and damage the three - headed monster.
Well, characters from Studio Ghibli movies could be really interesting. For instance, Totoro could be a strange and powerful ally in the Persona 3 world. His large size and gentle nature could be a contrast to the often - dark and brooding Persona 3 characters. He could use his magic to help them in battles against Shadows in unexpected ways, like creating huge gusts of wind to blow the Shadows away.
How about characters from a detective anime like Detective Conan? Conan's sharp mind and deductive skills could be really useful in the world of Fushigi Yuugi. He could help solve some of the mysteries that the characters encounter, especially those related to the political intrigue in the different kingdoms. His presence would also add an element of modern - day thinking to the more traditional fantasy setting of Fushigi Yuugi.
Gandalf from The Lord of the Rings. Imagine him showing up in the Marvel universe, using his magic to help the Avengers. His wisdom and powerful spells could be a great addition, especially in a battle against a powerful foe like Thanos. He could also offer different perspectives on heroism and sacrifice.