A possible idea for a MHA RWBY crossover fanfic is to explore the idea of semblance and Quirk evolution. The characters from both shows could train together and discover new ways to enhance their abilities. For instance, Izuku Midoriya could learn from Ruby about using her Crescent Rose in combat and in turn, show her how to better control her power flow. The cultural differences between the two worlds could also add depth to the story, like how the heroes in MHA are more publicly recognized compared to RWBY, and how the characters react to this disparity.
Another possibility is a crossover with the world of Naruto. The characters from MHA could participate in the Chunin Exams. Bakugo might be really into showing off his skills in this new and different kind of competition.
A great idea for an RVB RWBY crossover fanfic could be a tournament - style story. Characters from both universes are forced to participate in a huge tournament. This would allow for a lot of different match - ups between the characters. The Reds and Blues' comical and sometimes unorthodox fighting styles would contrast with the more refined and trained fighting styles of RWBY characters. It could also lead to some interesting friendships or rivalries forming during the tournament.
One idea could be to have the Spartans from Halo end up in the RWBY universe. They could team up with the RWBY characters to fight against a common enemy like the Grimm. Maybe the Spartans' advanced technology would be a big advantage in battles.
Well, a cool concept for an Overwatch RWBY crossover fanfic would be to focus on the technology aspect. Overwatch has a lot of advanced tech, and RWBY has its own unique Dust - based technology. The fanfic could explore how the two types of technology interact. For instance, Mercy's healing staff could be affected by Dust in the RWBY world, or Torbjörn could use RWBY - style materials to upgrade his turrets. And of course, the character interactions would be great. Winston and Zwei could be an interesting pair to write about.
Maybe the RWBY characters are on a quest in Skyrim to find a way back home. Along the way, they meet various characters like the Dark Brotherhood or the Thieves Guild. Ruby might befriend a young Nord who is also an aspiring warrior and learn some of the local combat techniques. Weiss could use her knowledge of Atlesian technology to improve some of the weaponry in Skyrim. Blake could uncover some secrets about the Daedric Princes that are related to the Grimm in some way, and Yang could participate in the Skyrim's famous brawls and earn a reputation as a fierce fighter.
One idea could be that Godzilla arrives in the RWBY world due to a strange dimensional rift. The Huntsmen and Huntresses initially see it as a huge threat and try to fight it. But then they discover that Godzilla is actually there to fight a common enemy, like a new type of Grimm that is immune to normal attacks but vulnerable to Godzilla's atomic breath.
One idea could be to have the RWBY characters team up with Halo Spartans to fight a common enemy. For example, a new type of Grimm that has been enhanced by Covenant technology. The different fighting styles of the RWBY characters, like Ruby's scythe - wielding and Halo Spartans' high - tech combat maneuvers, would create some really cool action scenes.
One idea could be that the Grimm in RWBY are somehow related to the beasts in Bloodborne. Maybe there's a common origin or a dark force that controls both. For example, the Grimm could be an earlier form of the Bloodborne beasts, and the Huntsmen and Huntresses have to deal with a new type of Grimm that has the characteristics of the Bloodborne creatures, like a more sentient and intelligent type of Grimm.
One interesting idea could be a crossover of different timelines within RWBY. For example, characters from the past meet the current ones and have to deal with the differences in their worlds. Another could be a crossover of different teams in unexpected ways, like Team RWBY having to team up with a rival team to face a common enemy that is more powerful than any they've faced before. And sometimes, there are crossovers that involve alternate versions of the characters, where their personalities or abilities are slightly different, which can lead to very unique and engaging storylines.
One idea could be that Naruto characters are transported to the RWBY world. Naruto himself could befriend Ruby and they could learn from each other's combat styles. For example, Naruto's chakra control might inspire Ruby to better control her own energy. Another plot could involve the Akatsuki from Naruto being interested in the Dust in RWBY's world and causing chaos to obtain it.