Ruby and Sans are quite popular. Ruby's energetic and positive personality contrasts well with Sans' lazy - yet - deep - thinking nature. Their interactions can be really interesting as they come from such different worlds but share a certain sense of humor. Another popular pairing is Weiss and Papyrus. Weiss' elegance and determination can play off Papyrus' over - the - top confidence and his own sense of honor in a really engaging way.
Naruto and Sans are quite a popular pairing. Naruto's energetic and determined nature contrasts with Sans' laid - back and somewhat mysterious attitude, making for an interesting dynamic. They could bond over their shared experiences of protecting their respective worlds.
Ruby and Frisk would be a really interesting pairing. Ruby is full of energy and determination, and Frisk has that unwavering kindness. They could learn a lot from each other, especially in terms of how they approach difficult situations and make decisions.
Naruto and Ruby would be an interesting pairing. Naruto's positive and energetic nature would contrast well with Ruby's somewhat more reserved but determined self. They could bond over their shared goal of protecting their friends and worlds. Another great pairing could be Sasuke and Weiss. Sasuke's cool and brooding demeanor against Weiss' ice - cold exterior would make for some intense interactions. They could also learn from each other's combat styles. And then there's Kakashi and Blake. Kakashi's wisdom and experience as a ninja could help Blake with her own inner demons and her fight against the White Fang, while Blake could introduce Kakashi to the concept of the Faunus in the RWBY world.
Sans from Undertale and his Underswap counterpart are often a popular pairing. People like to explore how the two different versions of him interact, given their different personalities. Another popular one is Papyrus from Undertale and his Underswap version. They can have some really funny exchanges.
Ragna from Blazblue and Ruby from RWBY could be an interesting pairing. Ragna is a brooding anti - hero with a powerful combat ability, while Ruby is an optimistic and energetic young huntress. Their different personalities could lead to some great character interactions, like Ragna being a bit cynical at first but slowly being influenced by Ruby's positive attitude. Another interesting pairing could be a Persona user, say Yu from Persona 4, and Jin from Blazblue. Jin is a cold and reserved swordsman, and Yu could use his empathetic nature and Persona powers to try to break through Jin's icy exterior. And for a third pairing, Blake from RWBY and a Persona user like Akechi from Persona 5. Blake has her own secrets and a complex past, and Akechi's dual nature could create an interesting dynamic as they both have things they are hiding.
Another popular pairing could be Blake and Black Rock Shooter. Given Blake's own complex past and her stealthy combat style, when paired with Black Rock Shooter, it can create some really engaging storylines. They could share their experiences of dealing with inner demons and fighting for what they believe in.
Another potentially popular pairing could be Sasuke and Weiss. Sasuke's brooding nature and powerful abilities could be an interesting contrast to Weiss's more refined and ice - cold demeanor. Their interactions could lead to some intense and complex storylines in the fanfiction.
Blake and Brian could be an amazing duo. Blake, with her love for books and her complex past, and Brian, the intelligent dog who is also a bit of a philosopher. They could have deep conversations about ethics and morality, all while being in a world that is a mash - up of RWBY and Family Guy.
Yang and the special forces' hand - to - hand combat expert. Yang is already a powerful fighter in close - quarters combat. The combat expert could teach her new moves and ways to better control her strength, while Yang could show the expert how to use her Semblance to her advantage in combat.
Ruby and Julian. Ruby is full of energy and has her powerful scythe skills, while Julian is a brilliant scientist in Genlock. They could have an interesting dynamic where Ruby is constantly amazed by Julian's inventions and Julian is in awe of Ruby's combat abilities and her positive attitude in the face of danger.