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 from 2003 get transported to the 2012 universe and they have to deal with the different versions of their enemies. For example, the Shredder in the 2012 version might have some new powers or tactics that the 2003 Turtles aren't used to.

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 Danny's ghost powers start to malfunction in the TMNT's dimension, causing strange ghostly events that the turtles have to help him fix. Another could be a villain from Danny's world teams up with one of the TMNT's foes, forcing the two groups to work together. Maybe Danny accidentally gets sent to the sewers where the turtles live and they initially mistake him for a new type of mutant.

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.

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.

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 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.

One idea could be that as a girl, Leo has to face different challenges in leading the team. Maybe she has to deal with more doubts from others at first because she's female. But she overcomes them with her skills and determination.

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.