One of the most interesting pairings could be Ron and the Minions. Ron is used to being around strange and magical creatures, but the Minions would still be a whole new level of odd for him. Their love for food and getting into trouble could lead to some really funny situations. Also, Bellatrix and Edith. Bellatrix's wild and unpredictable nature meeting Edith's no - nonsense attitude would create a lot of tension and drama in the fanfiction.
Definitely Harry and Gru. Harry, with his experience in facing great evil, could teach Gru a thing or two about true heroism. And Gru, with his knowledge of elaborate heists, could show Harry some unique ways to get around obstacles. Another interesting pairing would be Luna and Agnes. Luna's dreamy and unique perspective would blend well with Agnes' innocence and curiosity.
I think Dumbledore and Dr. Nefario would be an interesting pair. Dumbledore, with his wisdom and knowledge of magic, and Dr. Nefario, with his scientific genius. They could have some deep conversations about the nature of power and how it's used in their respective worlds. And then there's Ginny and Margo. Ginny is a strong - willed witch, and Margo is a smart and sassy girl. They could form an unlikely friendship and get into all sorts of adventures together.
I think Harry Potter and Nick Burkhardt would be an interesting pairing. Harry has his experience with fighting dark magic and Nick has his knowledge of the Wesen world. They could learn a lot from each other. Harry could teach Nick about some of the more complex spells, while Nick could introduce Harry to the different types of Wesen and how to deal with them.
I think Luna Lovegood and Prompto would make a really fun pairing. Luna has her unique and somewhat otherworldly view of things, and Prompto is the cheerful and energetic one in the FFXV group. They could have some really interesting conversations about the strange creatures in both their worlds. Also, Severus Snape and Gladio could be an unexpected but fascinating pairing. Snape's dark and brooding nature contrasted with Gladio's tough and protective side.
Harry Potter and Lucy Pevensie would make an interesting pairing. Harry is used to being the hero in his own world, but Lucy has a unique kind of innocence and faith in Narnia. They could learn a great deal from each other. Harry could teach Lucy about more complex forms of magic, while Lucy could show Harry the power of believing without seeing, which is a big part of her relationship with Aslan.
Another great pairing would be Hermione and Bruce Banner. Hermione is extremely intelligent and book - smart, and Bruce Banner is a brilliant scientist. They could collaborate on studying the differences and similarities between magic and science. Hermione could help Bruce understand the complex theories behind magic, and Bruce could explain to Hermione some of the advanced scientific concepts he's been working on. Also, when Bruce turns into the Hulk, Hermione could use her magic to try and control or at least direct the Hulk's power in a more useful way.
Definitely Harry Potter and Spider - Man. Harry has this whole burden of being the Chosen One and having to deal with the wizarding world's problems. Spider - Man, on the other hand, is a young hero trying to balance his normal life with his superhero duties. They could bond over their shared experiences of being young and having a lot of responsibility thrust upon them.
Another interesting pairing would be Ron and Papyrus. Ron is known for his loyalty and his love for food, and Papyrus is this enthusiastic skeleton who loves cooking and making friends. They could bond over food, with Ron introducing Papyrus to some wizarding world delicacies like Butterbeer and Pumpkin Pasties, and Papyrus showing Ron his 'Spaghetti Surprise'. Their friendship could also be a source of comic relief in a more serious crossover story.
Hermione Granger and Weiss Schnee could be a great pair. Hermione is highly intelligent and studious, while Weiss is refined and also has a great deal of knowledge. They could bond over their love for learning and perhaps work together on some sort of magical - mechanical hybrid project. For example, combining Hermione's magic knowledge with Weiss' understanding of Dust to create something entirely new.
Steve and Ron would be a really fun pairing. Ron could introduce Steve to the wizarding world's food and traditions, and Steve could show Ron how to be a bit cooler and more confident in social situations. Also, Joyce and Molly Weasley would be an interesting pair. They are both strong mother figures, and it would be fascinating to see them bond over protecting their kids and dealing with the strange situations in both universes.
Hermione and Tamaki would make for a unique pairing. Hermione's intelligence and studiousness contrasted with Tamaki's flamboyant and somewhat naive personality. Tamaki could introduce Hermione to the world of charm and social graces, while Hermione could help Tamaki with his studies if he were to be in the Hogwarts environment.
I think Ron and Prussia would make a great pair. Ron has his insecurities but also his loyalty and humor, and Prussia has his pride and bravado. They could start off not getting along, but then find common ground as they face challenges together. Also, Luna Lovegood and Japan could be an interesting combination. Luna's unique view of the world and Japan's more reserved and traditional nature could lead to some really unique conversations and adventures.