The Terrible Trio in fanfiction could have a plot where they focus on ruining Batman's reputation. They start by framing him for crimes he didn't commit. They plant evidence and manipulate the media. They also could be involved in a plot to steal all of Gotham's valuable art pieces, not for money but just to spite the city and Batman who protects it. This would put Batman in a difficult position as he has to clear his name while also stopping the Trio from stealing the art.
One idea could be that the Terrible Trio targets Gotham's new high - tech research facilities. They plan to steal advanced technology to enhance their own criminal operations. Another plot could involve the Trio teaming up with a new, mysterious villain who has a vendetta against Batman and using their combined skills to try and finally defeat him. A third plot might be that the Trio discovers Batman's secret identity and tries to use it to blackmail him into leaving Gotham.
The Penguin could be the most interesting. He's got his devious mind and his connections in the criminal underworld. His umbrellas and other gadgets add a unique touch to his criminal activities. He could be the mastermind behind the Terrible Trio's plans, using his wits to outsmart Batman.
Maybe a story where they team up with some of the more heroic characters in the Undertale world to face a common enemy. It would be interesting to see how their personalities clash and blend during the cooperation. For example, they might initially have different approaches to fighting the enemy, but gradually learn from each other.
One idea could be exploring the origin of the Creation Trio's powers. Maybe they got their powers from an ancient and mysterious Pokemon or a powerful energy source in the Pokemon world. Another idea is to have them face a new, powerful enemy that threatens the balance of the Pokemon universe, and they have to combine their unique abilities to defeat it.
Perhaps the trio stumbles upon a prophecy that predicts the end of the wizarding world. They then have to search for clues all over the wizarding and Muggle worlds to stop this from happening. They might also encounter a group of rogue wizards who are trying to use dark magic to create a new world order, and the trio has to stop them before it's too late.
One idea could be a time - travel plot where the Golden Trio goes back in time to prevent certain dark events from ever happening. They could change the course of history and save many lives. Another could be a story where they have to face a new, powerful dark wizard who is even more cunning than Voldemort, and they have to rely on their unique skills and friendship to defeat him.
Perhaps they could start off as rivals in the fanfiction. Batman from the present is skeptical of Batman Beyond's more high - tech approach. But as the story progresses, they learn from each other and become a great team. For example, Batman could teach Batman Beyond some of his old - school detective skills, while Batman Beyond shows Batman new ways to use technology in combat and surveillance.
One idea could be exploring what if Bruce Wayne's identity as Batman was exposed accidentally by a new high - tech surveillance system in Gotham. Another could be a story where Batman has to take on a new identity temporarily to infiltrate a secret criminal organization that has been studying his every move as Batman.
A plot could involve a time - travel scenario where Batman and Supergirl are sent back in time to prevent a major event that would change the future of both their worlds. They would have to work together, using their different skills and knowledge of their respective eras.
One idea could be exploring the relationship between Batman and Robin in a more emotional depth. Maybe Robin is going through a tough time at school and Batman has to balance being a mentor and a crime - fighter. Another could be a time - travel plot where the Bat - family gets sent to different eras in Gotham's history and has to adapt and still fight crime.
One idea could be that Batman and Robocop team up to take on a powerful criminal organization that is using high - tech weaponry. They would combine Batman's stealth and detective skills with Robocop's firepower and law enforcement programming.