SpongeBob SquarePants. This is a very unexpected crossover. But think about it, his carefree and positive attitude in the face of danger could contrast greatly with the more serious and battle - hardened characters of Honkai Impact 3. Maybe he could accidentally end up in the Honkai world and his unique abilities (like being able to survive underwater) could be used in unexpected ways to help the Valkyries.
The Doctor from SCP Foundation. It would be really interesting to see how the chaotic and often dangerous world of SCP would interact with the universe of Honkai Impact 3. The Doctor's knowledge and often unethical experiments could bring a whole new level of conflict and mystery to the crossover.
How about including characters from Sailor Moon? It would be really interesting to see the Gokaigers interact with the Sailor Scouts. Maybe they could learn some new strategies from the Scouts' magic-based attacks.
Well, characters from Studio Ghibli movies could be really interesting. For instance, Totoro could be a strange and powerful ally in the Persona 3 world. His large size and gentle nature could be a contrast to the often - dark and brooding Persona 3 characters. He could use his magic to help them in battles against Shadows in unexpected ways, like creating huge gusts of wind to blow the Shadows away.
How about characters from a detective anime like Detective Conan? Conan's sharp mind and deductive skills could be really useful in the world of Fushigi Yuugi. He could help solve some of the mysteries that the characters encounter, especially those related to the political intrigue in the different kingdoms. His presence would also add an element of modern - day thinking to the more traditional fantasy setting of Fushigi Yuugi.
Gandalf from The Lord of the Rings. Imagine him showing up in the Marvel universe, using his magic to help the Avengers. His wisdom and powerful spells could be a great addition, especially in a battle against a powerful foe like Thanos. He could also offer different perspectives on heroism and sacrifice.
Well, Superman could be an unexpected character. Imagine Naruto and his friends trying to figure out Superman's powers. It would be a really interesting dynamic as Naruto's ninja skills would seem so different compared to Superman's superhuman abilities.
How about Goku from 'Dragon Ball Z'? He's a powerful and pure - hearted character. If he were to be in a Death Note crossover, he would likely be very confused by the concept of the Death Note at first. His sense of justice is strong, but he would never consider using the Death Note to kill, which could create an interesting contrast with Light.
Alice from Wonderland. Her strange adventures in Wonderland could give her a unique perspective in Middle - earth. She might not be afraid of the strange creatures in Middle - earth as she has already faced the oddities in Wonderland. Maybe she could even make the trolls and orcs less menacing with her innocent charm.
Sonic the Hedgehog could be an unexpected addition. His super - speed could be a real challenge for the Mortal Kombat fighters. Another one could be Mario. He may seem out of place, but his jumping and power - up abilities could create some really interesting fight scenes in the Mortal Kombat world.
Sonic the Hedgehog could be an unexpected addition. His super - speed could be a great asset in the fast - paced battles that often occur in Chrono Trigger's world. He could race through time portals and help the gang outwit their enemies.
How about Hello Kitty? It might seem really strange, but in a fanfiction crossover, she could be turned into a powerful fighter. Maybe she has some cute but deadly attacks like throwing heart - shaped bombs. Also, Jack Skellington from 'The Nightmare Before Christmas' could be an unexpected addition. His spooky abilities and unique look would make for an interesting encounter with the 'King of Fighters K' cast.