Characters from other anime with magical or spiritual elements, like Naruto's Sasuke. Haku's water - based powers and Sasuke's fire - based powers could create an interesting power dynamic in a crossover story, and their different personalities could lead to a lot of conflict and growth.
Chihiro is often paired with Haku in crossover fanfiction. Since they have an existing relationship in the original story, it's easy to expand on it in a crossover scenario, like in a modern - day AU (Alternate Universe) where they have to deal with new challenges together.
Some might pair Haku with characters from other Studio Ghibli films. For instance, Totoro could be an interesting pairing. The contrast between Haku's more serious nature and Totoro's gentle and whimsical character could lead to some really fun and heartwarming stories.
Cthulhu is often paired with Nyarlathotep. Since they are both from the Lovecraftian mythos, their combined presence can create a much darker and more chaotic story. Another character could be Sherlock Holmes. The contrast between Holmes' rational mind and Nyarlathotep's otherworldly chaos makes for an interesting dynamic. Holmes would try to solve the mystery of Nyarlathotep's appearance and actions, while Nyarlathotep would be constantly trying to undermine Holmes' sanity.
One popular character is probably Gandalf from 'The Lord of the Rings'. The contrast between the Emperor's more militaristic and scientific approach and Gandalf's more magical and guiding role can create interesting stories. They could either be allies or have ideological clashes.
Lucario is also a popular choice to be paired with Pikachu in crossovers. Lucario has its own unique abilities related to sensing and combat. When combined with Pikachu's electric attacks, they can form a formidable team. The contrast between Lucario's more serious and stoic nature and Pikachu's cute and energetic personality also adds depth to the story.
Batman is a very popular character to pair with Superman in crossover fanfics. Their dynamic is well - known in the DC universe, with Batman being more of a dark and brooding detective while Superman is the all - powerful alien. Their different personalities and methods of crime - fighting make for great story material.
Octavia is also a character who gets paired a lot in crossovers. If there's a crossover with a show like 'Once Upon a Time', she could be paired with a character like Regina. The contrast between Octavia's warrior - like nature and Regina's more complex, magical personality would make for a great story. And of course, Murphy is often paired in crossovers. He could be paired with a character from a show like 'Falling Skies', and their shared experiences of being outsiders in their respective worlds could lead to an interesting relationship.
Stan can also be paired with Kenny. Stan's more moral - centered character can contrast with Kenny's somewhat nihilistic view of his own mortality. In a crossover with a post - apocalyptic world, Stan might be trying to find a way to save humanity while Kenny is just along for the ride, but still manages to survive in the most unexpected ways.
Zoro is another popular character. He and Luffy have a strong bond, and in Gear 5 fanfiction, they might fight together in a new and more coordinated way. Zoro could be using his swordsmanship to complement Luffy's wild and unpredictable Gear 5 attacks, creating a powerful combination against their enemies.
Alice Angel is often paired with Baby Bendy. Their interactions can range from her being a sort of mother figure to him, guiding him through the dark and twisted world, to more complex relationships where they might have conflicting goals but still a connection.
Another popular character to be paired with the 'brother of Naruto' is Hinata. The brother could be protective of Hinata's relationship with Naruto or he could develop his own feelings for her, creating a love triangle situation which adds a whole new layer of drama to the fanfiction.
Luigi is often paired with Vampire Waluigi in fanfiction. Since they are counterparts in the original Mario universe, it creates an interesting dynamic in the vampire - themed stories.