Definitely Legolas and Will Turner. Legolas with his amazing archery skills could teach Will some new techniques, and Will could show Legolas the ropes of being a pirate. They both have a sense of honor and loyalty, so they would make an interesting duo.
Arwen and Elizabeth Swann could be an interesting pairing. They are both strong - willed and intelligent women. Arwen could bring her elven wisdom and grace to Elizabeth, and Elizabeth could show Arwen how to be more assertive in a world full of men. They could team up to face threats that are both magical (from Lotr) and piratical (from Potc).
One idea could be that the One Ring somehow ends up in the world of Pirates of the Caribbean. Jack Sparrow, being the wily character he is, gets wind of its power and decides to either use it for his own gain or sell it to the highest bidder. The Fellowship, in turn, has to track it down in this strange new world full of pirates, sea monsters, and cursed treasures.
Naruto and Aragorn would be an interesting pairing. Naruto is a young hero full of energy and determination, while Aragorn is a battle - hardened and noble leader. They could learn a great deal from each other. Naruto could show Aragorn his unique ninja skills, and Aragorn could teach Naruto about leadership and honor.
I think Naruto and Frodo would be really interesting. Frodo has this burden of the One Ring and Naruto has his own struggles with the Nine - Tailed Fox. They could bond over their heavy responsibilities and Naruto could use his skills to protect Frodo on his journey.
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.
One idea could be to have the characters from Narnia and LOTR meet in a magical realm that exists between their two worlds. For example, Frodo and the hobbits could encounter Aslan. Another could be a story where the One Ring somehow ends up in Narnia and the Narnians have to deal with its corrupting influence, while Aragorn and his companions come to Narnia to help. Maybe the White Witch could team up with Sauron, creating a more powerful and menacing villain for the combined forces of Narnia and Middle - earth to face.
One possible plot could be that Naruto and his friends are somehow transported to Middle - earth. Naruto, with his never - give - up attitude, could inspire the hobbits on their journey. Maybe Naruto's chakra could be seen as a new form of magic in Middle - earth. His shadow clones could be used to confuse the orcs, just like how they confuse his enemies in the Naruto world. And the characters from LotR could learn about the concept of ninja and their unique skills from Naruto and his comrades.
Here's an idea. Buffy and Xander end up in Lothlórien. The elves are initially suspicious but then realize they are there to help. Buffy could use her agility and strength to assist in defending the forest. In another scenario, the Nazgûl could cross over to Buffy's Sunnydale. This would be a huge threat, and Buffy would have to use her knowledge of fighting demons along with the help of her friends and the weapons of Middle - earth (if they can get them) to defeat these powerful enemies.
Well, imagine that the One Ring has a strange connection to the chakra in Naruto's world. The Fellowship discovers that Naruto has a unique ability to resist the ring's power due to his strong will and chakra control. So they ask for his help in destroying the ring. Along the way, Naruto teaches the hobbits some basic self - defense ninja moves.
A possible plot is that Conan is brought to Middle - earth by a powerful magic accident. He lands in the Shire and is initially confused by the hobbits' way of life. But when he learns about the threat of Sauron, he decides to help. He teams up with Aragorn and they form an unlikely duo. Conan's no - nonsense attitude and Aragorn's leadership skills complement each other as they lead an army against Sauron's forces.
A lesser - known but excellent piece is 'Ringbearer Buffy'. Here, Buffy is somehow made into a ringbearer. It's a unique take on both franchises. The story delves deep into how Buffy's personality and her experiences as a slayer would affect her role in the quest to destroy the One Ring. It has some great character development and some really intense action scenes.