I think Frodo and Lucy would make an interesting pairing. Frodo is burdened with the One Ring and has seen a lot of darkness, while Lucy is full of innocence and hope. Their interactions could show how the two different worlds' outlooks can influence each other. For example, Lucy's unwavering faith might give Frodo some new strength in his fight against the Ring's power.
Aragorn and Peter. Both are leaders in their respective worlds. Aragorn is a ranger, a skilled warrior, and a king in waiting. Peter is a king in Narnia. They could exchange leadership strategies and fight side by side in a great battle. Maybe Aragorn could teach Peter some of his stealth and tracking skills, and Peter could show Aragorn how to lead with the kind of courage that comes from being a young but determined king.
Saphira, Eragon's dragon, and Gwaihir, the great eagle in Lord of the Rings. These two powerful flying creatures could form an alliance. They could communicate in their own ways and work together to provide aerial support during battles, as well as help in transporting important characters across great distances in Middle - earth and Eragon's world.
I think Lucy from Narnia and Frodo from LOTR would make an interesting pairing. Lucy has her own kind of innocence and faith, which could be a contrast to Frodo's burdened and determined nature. She might be able to offer him a different perspective on his quest, and he could show her the more complex and dangerous world of Middle - earth.
Harry Potter and Lucy Pevensie would make an interesting pairing. Harry is used to being the hero in his own world, but Lucy has a unique kind of innocence and faith in Narnia. They could learn a great deal from each other. Harry could teach Lucy about more complex forms of magic, while Lucy could show Harry the power of believing without seeing, which is a big part of her relationship with Aslan.
Naruto himself would be really interesting. His boisterous personality and never - give - up attitude would be a contrast to the more solemn characters in 'Lord of the Rings'. He could bring a new energy to the story, and his unique jutsu would make him a force to be reckoned with in Middle - earth.
I think Legolas could be really interesting. In 'The Hobbit', there are no elves from Mirkwood really involved in the story in the way Legolas is in 'The Lord of the Rings'. So, if you cross over the two, you could explore how Legolas might interact with the dwarves in a different context, considering the historical tension between elves and dwarves. He could also use his skills as an archer in new and unexpected ways, perhaps influenced by the events in 'The Hobbit' that he hears about from Gandalf or other characters.
Another great crossover could be between Gandalf and Urahara. Gandalf is a wise and powerful wizard, and Urahara is a very intelligent and somewhat mysterious character in Bleach. They could share their knowledge of magic and strategy. Gandalf might be intrigued by Urahara's unique inventions and scientific approach to spiritual matters, while Urahara could learn from Gandalf's vast experience and wisdom in dealing with different races and powers.
Yukari (from Persona 3) and Chie (from Persona 4). Yukari is very outspoken and has a bit of a sarcastic side, while Chie is energetic and a bit of a tomboy. Their different personalities could lead to some really fun and comical interactions, especially when they're facing Shadows together or just hanging out in the school setting.
One idea could be that the characters from Middle - earth accidentally stumble into Narnia through a magical portal. For example, Aragorn and Legolas could find themselves in the middle of the Narnian forest and team up with the Narnians to fight a common enemy, like an ancient evil that threatens both worlds.
Definitely the Flash and Iron Man. Tony Stark's high - tech gadgets and intelligence combined with the Flash's super - speed would make for some really cool scenes. They could work together on building some sort of super - fast vehicle or weapon. Another interesting pairing would be the Flash and Captain America. Steve Rogers' leadership and combat skills along with the Flash's speed could be a great combination for taking on enemies. The Flash could quickly get Steve into strategic positions during battles.