Some concepts involve crossing DDLC with classic literature. For example, a crossover with 'Pride and Prejudice'. Monika could be like Elizabeth Bennet, intelligent and strong - willed. The interactions between the DDLC characters would then be filled with the same kind of social intrigue and romantic tension as in the original novel.
One interesting concept could be creating unique OCs (Original Characters) with their own backstories that interact with the existing DDLC (Doki Doki Literature Club) characters in unexpected ways. For example, an OC who is a transfer student and has a mysterious past that somehow links to the club's secrets.
One interesting plot could be that the main character from DDLC, say, the protagonist, gets transported into the Undertale universe. They could start in the Ruins and interact with Toriel. Since the DDLC character is used to a different kind of world, their reactions to the monsters and the unique magic in Undertale would be fun to explore. Maybe they could try to use their knowledge from DDLC to solve some of the problems in Undertale, like trying to understand the nature of EXP and LOVE in the context of their own experiences.
I think Monika would be really interesting. In DDLC, she has that self - awareness and a certain level of power over her world. If she were in Undertale, her attempts to understand the very different rules of that world would be fascinating. She might try to use her powers to change things, but in Undertale, the concept of determination and the power of the player is very different. So seeing her interact with characters like Flowey, who also has some unique powers and knowledge, could lead to some really intense and thought - provoking scenes.
One interesting concept could be Shreck crossing over with other fairytale characters in a modern setting. For example, Shreck meeting characters from 'Cinderella' in a bustling city. It can create humorous and unexpected interactions, like Shreck's gruff nature clashing with Cinderella's elegance.
One interesting concept could be the combination of Ben 10 000's powers with other fictional universes. For example, if he were to cross over with the DC universe, seeing how his alien forms interact with super - heroes like Superman or Batman. Maybe his Four Arms form could have an epic battle with Doomsday.
Well, a lot of fgo crossover fanfiction involves different historical periods colliding. Say, a crossover with the Roman Empire era and the modern day in the fgo world. Servants from different eras teaming up or facing off against each other can create really engaging storylines. Also, crossovers with other JRPGs like 'Final Fantasy' often bring in unique magic systems and character designs that add a whole new dimension to the fgo fanfiction.
Another concept might be a crossover with a superhero universe. Picture the Metalocalypse band members having to deal with superheroes and villains. They could use their music in unexpected ways, like using a powerful guitar solo to stun villains or inspire superheroes in battle.
A third concept could be a crossover with a historical era. Picture Kidomaro in ancient Rome or medieval Europe. He would have to deal with the social norms, different forms of combat, and the overall culture of that time period. This would likely lead to some very unique and engaging storylines as he tries to find his place in a world so different from his own.
In Avatar 2009 crossover fanfiction, a cool idea is a crossover with a post - apocalyptic setting. The Na'vi could be faced with the challenges of a world destroyed by humans in a different way. They might have to deal with new threats and also learn from the survivors of the apocalypse. Also, a crossover with a superhero universe could be fascinating. Picture the Na'vi getting superpowers or having to deal with superheroes coming to Pandora.
One interesting concept could be a crossover with the Men in Black. Imagine the Ghostbusters teaming up with the MIB agents to deal with paranormal entities that are also of alien origin. They would have to combine their different technologies and ways of handling the supernatural and extraterrestrial.