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.
One possible plot could be that Eragon somehow gets transported to Middle - earth. He could meet Aragorn and learn from his leadership skills. Maybe they would join forces to fight a common enemy like a new breed of dark creatures created by a combination of Sauron's magic and the dark forces from Eragon's world.
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.
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.
A crossover with the Star Wars universe would also be cool. The Jedi could be like the wizards in Middle - earth. Maybe Aragorn could learn some lightsaber skills from the Jedi and use them against the orcs. And the Force could have an interesting interaction with the magic in Middle - earth.
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.
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 concept could be that a character from Lord of the Rings, like Legolas, somehow gets transported to the world of Prototype. There, he would have to adapt to the modern - day setting and deal with the infected. He could use his archery skills and elven agility in a completely different environment. His presence might also cause a stir among the military and scientific communities in the Prototype world, as they try to figure out who he is and where he came from.
Another interesting concept is that Vlad is a lost hero from a far - off land who arrives in Middle - earth. He could use his skills in combat and his knowledge of dark magic to help the Fellowship. For example, he might be able to use his vampiric speed to quickly scout areas or use his charm abilities to deceive the enemy. He could also have a complex relationship with Aragorn, either as a rival or an unexpected ally.
There's also 'The Lord of the Rings meets Harry Potter'. In this fanfiction, the magical worlds collide. Frodo and Harry Potter end up on a quest together, with Frodo's courage and Harry's magic making for an exciting adventure. It's interesting to see how the different magic systems interact.
Thomas and Twilight Sparkle. Thomas is a simple, hard - working engine, while Twilight is a studious and powerful unicorn. Their different natures could lead to some really interesting interactions. For example, Thomas could teach Twilight about the value of physical work and Twilight could introduce Thomas to the magic of knowledge.