Well, Prussia (Gilbert Beilschmidt from Hetalia) and Jean (from Attack on Titan) might be paired. Prussia has that over - the - top, boastful personality, and Jean has his own pride. They could start off as rivals but then grow to respect each other. And then there's Japan (Kiku Honda from Hetalia) and Sasha (from Attack on Titan). Japan is known for his calm and collected nature, while Sasha is more impulsive and food - loving. Their interactions could be really fun, like Japan trying to understand Sasha's love for food and Sasha being intrigued by Japan's culture.
Lovi (Lovino Vargas from Hetalia) and Levi (from Attack on Titan) could be a likely pair. They both have that tough - exterior and are often seen as no - nonsense characters. Their interactions could be full of bickering and grudging respect. Another possible pair could be America (Alfred F. Jones from Hetalia) and Eren (from Attack on Titan). They are both quite headstrong and have a strong sense of justice, so they might team up to fight the Titans and try to bring about change in the world.
I think Italy (Feliciano Vargas from Hetalia) and Armin (from Attack on Titan) could be paired. Italy is often portrayed as more on the naive and friendly side, while Armin is very intelligent. Their combination could be interesting, with Armin coming up with plans and Italy providing the emotional support or some unexpected solutions. Also, Germany (Ludwig Beilschmidt from Hetalia) and Mikasa (from Attack on Titan) could be a good pair. They are both highly disciplined and strong, and they would probably work well together in combat against the Titans.
Percy Jackson and Carter Kane would be a great pair. Percy is used to the Greek mythological world and its challenges, while Carter has a deep understanding of Egyptian magic and mythology. Their different perspectives could lead to some interesting teamwork, like when they face a monster that has aspects of both Greek and Egyptian mythology, such as a Sphinx with the ability to use water attacks like a Greek hydra.
Ron and Uryu might be paired. Ron has his own insecurities but also his moments of great courage, much like Uryu. They could bond over their skills in combat, Ron with his magic and Uryu with his Quincy powers.
Mabel and Marco could be an interesting pair. Mabel is all about fun, friendship, and having a good time. Marco is more of a practical and responsible character. Their interactions could be really comical as Mabel tries to get Marco to loosen up and have more fun, while Marco tries to keep Mabel in line when things get too wild.
Well, a cool concept could be the power dynamics. In Hetalia, each nation has its own strengths and weaknesses. When combined with the world of Attack on Titan, those strengths and weaknesses could play out in interesting ways. For instance, a nation known for its military strategy in Hetalia might come up with new battle plans against the Titans. Also, the idea of the Titans being influenced by the Hetalia characters' personalities. Say, a really goofy Hetalia character might make a Titan act in a less menacing way just because it's so confused by the character's antics.
Eren and Raleigh would be likely to team up. Eren has his powerful titan - shifting abilities which could be useful in close - combat situations against both titans and Kaiju. Raleigh, with his experience in piloting a Jaeger, could guide Eren on how to better use his powers in coordination with the large - scale technology of the Jaegers. They could form a strong bond as they both have a strong sense of justice and a desire to protect their respective worlds.
Naruto and Bart could be a likely pair. Both are mischievous in their own ways. Naruto is always getting into trouble with his pranks in the ninja academy, and Bart is constantly causing chaos in Springfield. They could get up to all sorts of antics together, like pulling pranks on the other characters in both universes.
Harry Potter and Nate Ford could be a likely pair. Harry's experience with facing great evils and his leadership skills combined with Nate's strategic mind in planning heists would make for an interesting dynamic. They could learn from each other's methods of problem - solving.
Buffy and Luke Skywalker could be an interesting pair. Buffy is a strong fighter and leader in her world, and Luke is a key figure in the Star Wars universe. They could learn from each other's combat styles and leadership skills.
Master Chief from Halo and Apollo from Battlestar Galactica could be an interesting pair. Master Chief is a super - soldier with incredible combat skills, and Apollo is a skilled pilot and military leader. Their different skillsets could lead to some great teamwork in a crossover story. Another possible pair could be Cortana and Starbuck. Cortana is an AI with vast knowledge, and Starbuck is a brash but talented pilot. They could have some really interesting exchanges, with Cortana providing strategic advice to Starbuck.
The Doom Slayer and Commander Shepard are likely to be paired. They are both iconic heroes in their respective universes. Shepard is a strategic leader, while the Doom Slayer is a force of pure destruction. Their interactions could lead to some really interesting storylines.