Ruby could be paired with Eragon. Ruby's leadership and combat skills along with her silver eyes' power could complement Eragon's dragon - rider abilities. They could go on quests together, with Ruby's speed and Eragon's dragon - powered flight making them a formidable team.
Blake and Murtagh could be an interesting pair. Blake's stealth and her cat - like abilities could work well with Murtagh's more brooding and powerful character. They might find common ground in their somewhat outsider status within their respective worlds and form a bond while facing challenges together.
Yang and the Yellow Ranger. Yang is a strong and fiery character in RWBY, known for her brawling combat style. The Yellow Ranger in many Power Rangers shows is also a strong fighter. They could bond over their love for a good fight and share tips on how to improve their physical combat skills. Plus, their personalities are quite compatible, with both being bold and confident.
Ruby and Goku could be a likely pair. Ruby is young and full of potential, much like Goku was when he started his journey. Goku could be a mentor - like figure to Ruby, teaching her about Ki and new combat techniques. Another pair could be Weiss and Vegeta. Weiss is from a noble family and has a sense of pride, similar to Vegeta. They could have an interesting dynamic where they initially clash due to their strong personalities but then grow to respect each other. Yang and Trunks could also be paired. Yang is a strong and fearless fighter, and Trunks has his own badassery. They could team up in battles and share their experiences of growing up in tough situations.
Percy Jackson and Carter Kane would be a great pair. Percy is used to the Greek mythological world and its challenges, while Carter has a deep understanding of Egyptian magic and mythology. Their different perspectives could lead to some interesting teamwork, like when they face a monster that has aspects of both Greek and Egyptian mythology, such as a Sphinx with the ability to use water attacks like a Greek hydra.
Naruto and Bart could be a likely pair. Both are mischievous in their own ways. Naruto is always getting into trouble with his pranks in the ninja academy, and Bart is constantly causing chaos in Springfield. They could get up to all sorts of antics together, like pulling pranks on the other characters in both universes.
Perhaps the characters from RWBY could inherit some of the dragon - related powers from the Inheritance Cycle. This would create a whole new dynamic for their battles and character development. They might gain abilities like telepathy with dragons or the power to use dragon - based magic.
Another possible pairing could be Sasuke and Elsa. Sasuke has his own dark past and a brooding personality. Elsa also has her own internal struggles with her powers. They could bond over their shared experiences of having to control something within themselves that others might fear. And their cool and somewhat aloof demeanors could make for an interesting dynamic.
Arya is an interesting character to write about. She has a complex personality and a lot of responsibilities. Fanfic writers can explore her feelings towards the humans more, especially considering her elven heritage. Also, Murtagh. His tortured past and his complex relationship with Eragon provide a rich ground for storytelling. Writers can explore what could have been if he had made different choices or if he had been given more support early on.
Lovi (Lovino Vargas from Hetalia) and Levi (from Attack on Titan) could be a likely pair. They both have that tough - exterior and are often seen as no - nonsense characters. Their interactions could be full of bickering and grudging respect. Another possible pair could be America (Alfred F. Jones from Hetalia) and Eren (from Attack on Titan). They are both quite headstrong and have a strong sense of justice, so they might team up to fight the Titans and try to bring about change in the world.
Ron and Uryu might be paired. Ron has his own insecurities but also his moments of great courage, much like Uryu. They could bond over their skills in combat, Ron with his magic and Uryu with his Quincy powers.
Yoko from Gurren Lagann and Hermione Granger could be paired. Yoko is a strong and independent female character, and Hermione is brilliant and resourceful. They could team up to face challenges, with Yoko providing her combat skills and Hermione her vast knowledge of magic. Their combination could be a force to be reckoned with in the fanfic.