One idea could be to have Ben Tennyson end up in the Young Justice universe by accident. Maybe his Omnitrix malfunctions during a fight and transports him there. He could then team up with the Young Justice heroes to fight a common enemy like the Light or some new villain that's a threat to both universes.
In a Ben 10 and Naruto fanfic, their powers would be a great combination. Ben has the ability to transform into various alien forms, each with unique powers. Naruto has his chakra and his powerful jutsu. They could learn from each other. For example, Ben could teach Naruto about some of the alien technologies, while Naruto could teach Ben about chakra control and the ninja way.
One idea could be that Ben Tennyson, while on a mission in another dimension, accidentally lands in the X - Men's universe. His Omnitrix starts acting strangely due to the different energy signatures there. The X - Men initially see him as a threat but then realize he could be an ally in fighting a common enemy, like a powerful mutant - alien hybrid that is causing chaos. Ben could transform into some of his alien forms to help the X - Men in battles, and there could be interesting interactions between the different characters, like Gwen and Rogue comparing their powers.
One possibility could be that Ben Grimm, as The Thing, brings his unique strength and loyalty to the Avengers. His rocky exterior could be a great asset in battles, like providing cover for his teammates. He might also have some interesting interactions with the other Avengers, especially those with a sense of humor like Tony Stark. They could make some witty remarks about his appearance while also respecting his power.
One unique feature is the combination of different power systems. Ben 10 has his alien forms with various powers, and Bakugan have their own unique abilities based on their types. When these are combined in a fanfic, it creates really interesting battle scenarios.
One popular idea is crossovers with other popular animated shows like Teen Titans. It's exciting to see the Ben 10 characters interact with the Titans. Another idea could be a crossover with the Powerpuff Girls, imagining how the different powers and personalities would clash or cooperate. Also, crossovers with the Justice League can be really cool, as Ben 10's alien forms could bring a new dynamic to the superhero team.
One interesting concept could be the combination of the unique alien forms in Ben 10 with the dark and complex lore of Warhammer. For example, how would an Omnitrix - transformed alien interact with the various factions in Warhammer, like the Space Marines or the Orks? Another concept might be the power dynamics. Ben's powers are usually used for good, but in the Warhammer universe, the lines between good and evil are often blurred. So, it would be fascinating to see how he navigates this new moral landscape.
Well, Ben is the central figure. But don't forget about Kevin Levin. His ability to absorb and use different forms of energy could be very relevant in the Warhammer universe filled with all kinds of strange energies. In Warhammer, a Chaos Sorcerer could be a main character. The way his dark magic would interact with Ben's powers and the overall plot would be full of potential. Also, Rook Blonko from Ben 10 could be important. His skills and loyalty could add a different dynamic to the story as they explore the Warhammer universe together with Ben.
One possible plotline is that Ben Tennyson accidentally gets transported to the world of Fairy Tail. He has to figure out how to use his Omnitrix in a world full of magic. Another could be that the Fairy Tail guild discovers an alien device similar to the Omnitrix and they try to figure out how it works.
One idea could be Ben Tennyson using his Omnitrix to team up with Spider - Man. Ben could transform into XLR8 to chase down villains while Spider - Man swings through the city. Another could be having Four Arms help the Hulk in a battle, combining their brute strength. And perhaps Heatblast could join forces with the Human Torch to fight a fire - based villain.