Daenerys Targaryen in the 'Vampire Diaries' world would be fascinating. Imagine her arriving in Mystic Falls with her dragons. She'd be a force to be reckoned with. The vampires would be both intrigued and perhaps a bit intimidated by her. She could use her leadership skills and the power of her dragons to navigate the supernatural politics of Mystic Falls, and might even form an alliance with some of the vampires against common enemies like the werewolves or other dark forces.
I think Pam from 'True Blood' would be a great crossover character. She's sassy and loyal to Eric. In 'The Vampire Diaries', she could add a new dimension to the female characters. She could form an unlikely friendship with Caroline, for example. Pam could also bring her own sense of vampire style and attitude to the more traditional vampire world of 'The Vampire Diaries', causing some raised eyebrows and a lot of interesting interactions.
Definitely Ragnar and Tyrion. Ragnar is a fierce and intelligent Viking leader, and Tyrion is a clever and witty character in Game of Thrones. Their interactions would be full of banter and strategic planning. They could both learn a lot from each other's ways of dealing with power and politics.
Jaime Lannister would be an unexpected but interesting choice. He's a skilled swordsman with a complex personality. In the 'Hunger Games', he'd have to grapple with his own sense of honor and self - preservation. His relationship with other tributes could be full of drama, as he's used to the political and personal intrigues of the Seven Kingdoms. Plus, his golden hand could be a unique weapon or advantage in the arena.
Klaus Mikaelson would be a really interesting character to crossover. He has such a complex personality - part villain, part anti - hero. In The Vampire Diaries, he was a major threat, but in The Originals, we see more of his vulnerable side. Bringing him back to Mystic Falls in a crossover would create a lot of drama. His power and his history with the characters there would make for some great storylines.
I think Jack Sparrow from 'Pirates of the Caribbean' would be really cool to cross over with Hercules. Jack's wily and unpredictable nature would contrast with Hercules' more straightforward heroism. They could be on a quest for a magical artifact that has the power to either save or destroy the world. It would be full of adventure, humor, and unexpected twists.
I think Gandalf would be a very interesting character to cross over. He has so much wisdom and power in LOTR. In the Harry Potter world, he could share his knowledge of different magics and perhaps help Dumbledore in his fight against Voldemort. He could also introduce the concept of the greater good in a more profound way to the young wizards and witches.
Definitely Doctor Strange. He already has a deep understanding of magic in the Avengers universe. In the Harry Potter world, he could exchange knowledge with the wizards, learn new spells, and maybe even help improve the defenses of Hogwarts. He could also have some really cool battles against the dark wizards using his unique combination of magic and martial arts.
Hermione Granger would be really interesting. She could bring her intelligence and magic skills to the OITNB world. She might start a library or a study group for the inmates, teaching them about magic and also helping them with their own educational pursuits. Her strong - willed and determined nature would make her a force to be reckoned with in the prison environment.
Aquaman himself is often a popular choice. His unique abilities and his role as a king make him an interesting character to insert into the Game of Thrones universe. He could potentially interact with various characters in Westeros.
Ciri and Daenerys Targaryen. Ciri has magical powers and is a strong female character. Daenerys has her dragons and is a powerful leader. They could meet and form an alliance. Ciri might be interested in Daenerys' dragons and Daenerys could be intrigued by Ciri's magic. Together they could change the power dynamics in a fanfiction world.