A possible plot is that the Teenage Mutant Ninja Turtles end up in Gotham City by accident. Batman initially views them as threats but then realizes they are on the same side when they start fighting a gang that is using mutagen - like substances. Or perhaps there's a story where Batman's gadgets and the Turtles' ninjutsu skills are pitted against each other in a battle of wits and strength, but then they have to combine forces when a greater threat emerges from the sewers.
Well, there could be a fanfiction plot where the Teenage Mutant Ninja Turtles are brought to Gotham by a mad scientist who wants to study their unique abilities. Batman gets involved when the Turtles start causing a bit of chaos in the city while trying to find their way back home. As they interact, they learn from each other's fighting styles and eventually join forces to take down the scientist, who has also created some mutated monstrosities in the city.
One idea could be exploring the turtles' origin in more depth from a different perspective. Maybe a new character discovers a hidden aspect of their mutation process.
One idea could be a story where the turtles have to blend in as humans in a high school setting. They could struggle with normal teenage things like exams and dating while also hiding their turtle identities.
One idea could be a story where the Teenage Mutant Ninja Turtles discover a hidden mecha technology in the sewers. They have to figure out how to use it to defeat a new, powerful enemy. Maybe it gives them new abilities like enhanced speed or the power to fly.
One idea could be that the Pokemon trainers are in the world of the Teenage Mutant Ninja Turtles. They could team up with the turtles to fight against a common enemy, like an evil organization that is trying to take over both the Pokemon world and New York. For example, Team Rocket could be working with some of the villains from the TMNT universe.
One idea could be a crossover with the Power Rangers. The Turtles and the Rangers could team up to fight a common enemy like an alien invasion. The Rangers' high - tech weapons and the Turtles' ninja skills would make for an exciting combination.
One idea could be a story where the turtles become human for a day and have to navigate high school. They'd struggle with normal teenage things like fitting in and dealing with bullies, all while trying to hide their turtle identities.
It's really hard to say. Batman has his incredible intellect, martial arts skills, and a vast array of gadgets. But the Teenage Mutant Ninja Turtles are no slouches either. They have their ninjutsu training and unique teamwork. If it's a one - on - one fight, Batman might be able to outwit and outmaneuver a single Turtle, but if all four Turtles gang up on him, they could overpower him with their combined strength and skills.
You could write a fanfic where the Teenage Mutant Ninja Turtles discover a hidden underground city beneath New York. In this city, there are mutants with different abilities and cultures. The turtles have to learn to navigate this new society while also facing a threat that wants to use the underground city's resources for evil. Or, a fanfic that focuses on the turtles' training. What if they had a new mentor who taught them a completely different style of martial arts? It would change the way they fight and interact with their enemies. Also, a story about the turtles getting shrunk to a tiny size and having to survive in a world that's now giant to them could be really interesting.
One interesting fanfiction could be about the turtles' adventures in a parallel dimension. Maybe they encounter alternate versions of themselves or face new villains that are unique to that dimension.
A really cool Teenage Mutant Ninja Turtles fanfiction might be set in a post - apocalyptic future. The turtles are the last hope for humanity against a powerful mutant overlord. They have to use their skills and wits to gather allies and find a way to defeat this ultimate enemy. This type of story could explore their growth and leadership in a dire situation.