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.
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.
Well, I think Green Lantern and Rock Lee would be an interesting pair. Green Lantern's power of creating constructs with his ring could be used in creative ways along with Rock Lee's taijutsu. Also, Wonder Woman and Hinata could be paired. Wonder Woman's combat skills and Hinata's Byakugan - enhanced fighting style would make for a great combination. And Flash and Kiba with his dog Akamaru could be a fun pair, with Flash's speed and Kiba's speed - based ninja techniques.
Naruto and Bella could be an interesting pair. Naruto's energetic and positive nature could contrast with Bella's more introverted and moody self. It could create a unique dynamic where Naruto tries to cheer up Bella and she, in turn, shows him the more complex emotional side of the Twilight world.
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.
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.
Sasuke and Sein could be an unexpected but fascinating pair. Sasuke's brooding and powerful presence might contrast with Sein's pure and guiding spirit. Their interactions could lead to some great character development for both of them.
I think Hinata and Rias could be paired up in some way. Hinata's gentle nature and her strong loyalty could complement Rias' leadership and determination. They might form an unexpected friendship or even a strategic alliance within the fanfiction's plot.
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.
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.
Luna and Neville would be another possible pair. They are both somewhat outcasts in their own ways in the Harry Potter world. In the fanfic, when the bottle lands on them, it could lead to a really sweet and heartwarming moment. They could bond over their shared experiences and unique perspectives on magic, and perhaps develop a deeper relationship.