Ranma and Goku would be really interesting. Goku's pure love for fighting and his simple - minded yet kind nature would contrast with Ranma's more complex and often flustered personality. They could have some really fun training sessions together. Also, Bulma might be fascinated by Ranma's ability to change gender and try to figure out how it works scientifically.
I think the interaction between Vegeta and Ranma could be intense. Vegeta is proud and strong - willed. Ranma would not back down easily either. They could have some epic battles or, in a strange turn of events, they might end up respecting each other's fighting abilities. And Chi - Chi might be really confused by Ranma's whole situation, especially his gender - changing thing.
One idea could be that Ranma somehow gets transported to the DBZ universe. He could end up training with Goku and learn the Kamehameha wave, but with his own Ranma - style twist. Maybe he uses his martial arts skills from his world to create a new fighting style combined with ki. Another plot could involve the Dragon Balls. Ranma might accidentally make a wish on them that gets him involved in a big battle against a powerful villain in the DBZ world.
Definitely the interactions between the two versions of Leonardo. The 2012 Leo is more light - hearted in some ways compared to the very serious 2003 Leo. They could have some great moments of leadership clashes and then learning from each other. For example, the 2003 Leo could teach the 2012 Leo some of his more stoic leadership techniques.
I think the interaction between Joker (from Persona 5) and Yu (from Persona 4) would be really interesting. They are both leaders of their respective groups, so they could exchange leadership strategies and learn from each other. Also, Morgana and Teddie would be hilarious together. Morgana's serious yet sometimes clueless nature and Teddie's over - the - top and comical personality would create some great comedic moments.
Definitely Joker and Makoto Yuki. Joker is the leader of the Phantom Thieves, very confident and strategic, while Makoto Yuki is a strong and silent type. Their leadership styles could clash or complement each other.
How about a Ranma crossover with Harry Potter? Ranma could be a foreign exchange student at Hogwarts. His martial arts could be a form of magic in the wizarding world. Or a crossover with Fullmetal Alchemist. Ranma might get involved in the search for the Philosopher's Stone or help the Elric brothers with their alchemical problems. There are so many possibilities for Ranma crossover fanfiction.
The interaction between Riku and Goku would be really interesting. Goku is all about raw power and the joy of battle, while Riku is more about strategy and out - thinking opponents. They could learn a lot from each other. Goku could teach Riku about the importance of physical strength and Riku could show Goku how to plan battles more carefully.
Well, a really cool concept could be a villain that threatens both the Naruto and DBZ universes. So, characters from both sides have to team up to defeat this powerful foe. Imagine Vegeta and Sasuke having to work together, despite their initial differences. Also, there could be a story where the Dragon Balls are somehow transported to the Naruto world, and Naruto and his friends try to figure out what they are and how to use them.
Gohan and Robin would be an interesting pairing. Gohan, with his intelligence and powerful fighting skills, could bond with Robin over their shared smarts and desire to protect their respective worlds. They could exchange knowledge about combat strategies and detective work.
Ranma and Gina could be an interesting pairing. Ranma's unpredictable nature due to his curse and Gina's no - nonsense attitude would create a lot of friction and also some great comedic moments. They could start off as rivals, constantly trying to one - up each other, but gradually develop a grudging respect.
I think Ranma and Priss would make an interesting pairing. Ranma's hot - headed and impulsive nature combined with Priss's tough and no - nonsense attitude could lead to some great interactions. They could start off as rivals, constantly trying to one - up each other in combat or in solving problems. Another interesting pairing could be Akane and Linna. Akane's strong - willed and sometimes stubborn personality could clash and also bond with Linna's more easy - going but determined nature.