What are some interesting plot ideas for a TMNT 2012 and 2003 crossover fanfiction?

One idea could be that the Turtles from 1987 end up in the 2003 universe and have to adapt to the darker and more serious tone. They could team up with the 2003 Turtles to fight a common enemy like the Shredder. The 1987 Turtles' more light - hearted and comical ways might initially clash with the 2003 Turtles' brooding nature, but they eventually learn from each other.

One idea could be that the Turtles end up in the Underground world of Undertale. They might have to navigate through the various regions, like Snowdin or Hotland, using their ninja skills. For example, they could use their stealth to avoid some of the more dangerous monsters. Another plot could involve the characters from Undertale being brought to the Turtles' New York. They would then have to deal with the Foot Clan and other threats in this new, strange environment.

One idea could be that the turtles from 2012 somehow get transported to the 2018 universe. They could be really confused by the different art styles and the new gadgets the 2018 turtles have. The 2018 turtles, on the other hand, would be intrigued by the more traditional look of the 2012 turtles. This could lead to some funny moments as they try to communicate and figure out how to get the 2012 turtles back to their own universe.

One idea could be that the Ninja from Ninjago are transported to the TMNT's world. They team up to fight a common enemy like the Shredder who has somehow got hold of some dark magic from Ninjago. The Ninja can show the Turtles their unique fighting styles and the Turtles can introduce the Ninja to the sewers of New York as a base.

One possible plot could be that the Teenage Mutant Ninja Turtles somehow end up in the Freddy Fazbear's Pizza place. Maybe they are investigating some strange disappearances that are rumored to be related to the animatronics. They could use their ninja skills to navigate the dark hallways and face off against the haunted animatronics. The turtles' unique personalities would add a fun dynamic, like Mikey being scared at first but then finding the whole situation exciting, while Raph is ready to fight from the start.

Perhaps a plot where Leo discovers some new powers or abilities that are related to his pregnancy. It could be something that he has to learn to control quickly. And then there could be a story arc about the team finding a way to ensure a safe delivery for Leo, which might involve seeking out some very rare or magical items.

One idea could be that Mikey and Shinigami team up to solve a mystery in the sewers that involves some strange magical creatures. They use Mikey's fun - loving nature and Shinigami's magic skills to figure things out.

A snake OC fanfiction could focus on a snake that was experimented on by the Kraang. It gains super - intelligent and psychic powers. The Turtles initially see it as a threat but then realize it just wants to find a place in the world. They help it control its powers and it becomes an ally. It could have a really cool design with purple and green scales from the Kraang experiments.

One idea could be a Winged OC who is from a different dimension and has the power to heal. The OC could encounter the TMNT during a battle where one of them is seriously injured. Another plot could be that the Winged OC is on a quest to find a lost artifact, and the TMNT get involved either by accident or because they also have an interest in the artifact. Or perhaps the Winged OC is a runaway from an evil organization that the TMNT are trying to take down, and they form an alliance.

Perhaps the mutagen that created the Turtles has some strange reaction when exposed to the Dragon Balls' energy. This could lead to new powers for the Turtles and a whole adventure about controlling and understanding these powers while also dealing with the Dragon Ball Z characters' reactions to them. For example, Vegeta might be initially suspicious and see the Turtles as a threat to his power status.