Gwen and Harry would be really interesting. Harry has his own set of skills and experiences with magic and fighting dark forces. Gwen has her alien powers. They could learn from each other. Harry could teach Gwen about the magical world, and Gwen could show Harry some of her cool alien gadgets and abilities.
Gwen and Dumbledore would also make for a great interaction. Dumbledore is so wise and knowledgeable. Gwen could be a bit of a mystery to him at first, but then he would start to understand her powers. He might even find ways to incorporate her abilities into the fight against Voldemort. Maybe he would ask Gwen to use her XLR8 form to quickly deliver important messages across Hogwarts in a time of crisis.
Hermione Granger and Alex Mercer would also have an interesting dynamic. Hermione is known for her intelligence and thirst for knowledge. She would be eager to study Mercer, his powers, and the science behind the Prototype virus. Mercer might be initially annoyed by her questions but would eventually come to respect her intelligence and might even learn a thing or two from her about the wizarding world.
Definitely Jack O'Neill and Harry Potter. Jack's military experience and his no - nonsense attitude would contrast with Harry's more idealistic and sometimes impulsive nature. They could learn a lot from each other. For example, Jack could teach Harry some combat strategies that don't rely on magic, while Harry could show Jack the power of believing in something intangible like magic.
Definitely Harry and Gaster. Harry is used to the magic in his world, while Gaster has his own set of abilities. Their meeting would be full of confusion, curiosity, and perhaps a bit of wariness. Another interesting interaction could be between Hermione and Gaster. Hermione would be eager to learn about Gaster's knowledge and would probably bombard him with questions.
A possible plot is that there is a threat in both worlds at the same time. Gwen and Harry have to team up, with Gwen using her alien powers and Harry his magic. They travel between the two worlds, trying to find the source of the threat. Gwen's Ghostfreak form could be used to spy on the enemies in the Harry Potter world without being detected easily.
Definitely Harry Potter and Rias. Rias is used to leading and being in control, but Harry has his own strong sense of justice and leadership. Their interactions could be full of power plays and mutual respect as they try to figure out how to work together.
I think Harry Potter and Batman would have an interesting interaction. Batman is known for his intelligence and detective skills, and Harry has his own brand of cleverness and magical knowledge. They could compare notes on how to solve mysteries and fight crime in their respective worlds.
Dumbledore and Shikamaru would be an unexpected but fascinating pair. Dumbledore, with his great wisdom and power, could be intrigued by Shikamaru's unique way of thinking. Shikamaru, on the other hand, would be in awe of Dumbledore's magical abilities and the mysteries of the wizarding world that Dumbledore represents. Their conversations could lead to new insights for both characters.
Dumbledore and Merlin would be a fascinating pair. Two powerful and wise wizards from different times. They could exchange ideas about leadership in the magical world, how to guide young wizards, and strategies for dealing with dark magic threats.
I think the interaction between Bruce Banner and Hagrid would be fascinating. Hagrid is used to dealing with all kinds of strange creatures, but the Hulk would be something entirely new. He would probably be both scared and intrigued. Also, Bruce and Snape could have an interesting dynamic. Snape's brooding and often misunderstood nature might resonate with Bruce. Snape could be interested in the scientific aspects of Bruce's transformation, while Bruce might be able to see through Snape's tough exterior to the good in him.
Definitely Harry and Rachel. Rachel is so ambitious and Harry has his own heroic journey. Their interactions could be about achieving their dreams. Harry could learn from Rachel's drive in the performing arts world, and Rachel could be inspired by Harry's selfless heroism.