Well, a cool plot could be that one of the thieves is actually working undercover for the police. So, while the two are planning heists together, the undercover thief is secretly trying to gather evidence against the other. But as time goes on, they form a real bond, and the undercover thief has to decide between loyalty to the law and loyalty to their newfound friend. Also, they could be stealing from a corrupt noble. This noble has been oppressing the poor, and the thieves see it as a Robin - Hood - like mission. However, the noble discovers their plan and sets traps for them all over the place.
One possible plot for a 'A Tale of Two Thieves Fanfiction' is that the two thieves are descendants of a long - lost guild of thieves. They discover a map that leads to the hidden treasure of their ancestors. Along the way, they face challenges like ancient traps and rival thieves who also want the treasure. The two thieves might have different skills. One could be great at picking locks and the other at sneaking around unnoticed. Their different skills help them overcome the obstacles. Another plot could involve them stealing a magical item that gives them the power to turn invisible, but it also has a side effect that makes them slowly lose their memories. They have to find a way to reverse the side effect while still using the item's power to pull off more heists.
Another plot could involve a prophecy that states only the one who can balance the power of the two swords can bring peace to the land. The protagonist is chosen to do this but faces many temptations and obstacles along the way, as there are those who want to use the swords for their own evil purposes.
A plot could revolve around a forbidden love between two characters from rival groups that wasn't explored in the original story. Maybe a character from the thieves' side and one from the more noble side fall in love and have to fight against all odds to be together.
How about a plot where the Phantom Thieves get trapped in a virtual world created by an evil hacker? In this world, their cognitive powers are limited, and they have to find a way to break free. They might meet some virtual characters who can either help or hinder them. It would be a battle of wits and skills as they try to escape and take down the hacker in the real world.
Another plot idea might be to focus on the lives of the common people in Paris during the revolution in a fanfic of 'A Tale of Two Cities'. Show how they are caught up in the chaos, their hopes, and their fears. For example, create a story about a young peasant who becomes a key figure in the revolution, but then starts to question the extreme violence.
Perhaps a story about a mystery within the abbey walls. For example, an ancient artifact goes missing and the characters have to use their wits and knowledge of the abbey's history to find it. It could involve exploring hidden passages and deciphering old clues. This would give a sense of mystery and intrigue to the fanfiction.
Another plot idea could be a what - if scenario. For example, what if one of the sisters had a different power? This could change the whole dynamic between them and the story. Say, if Elsa had the power to control time instead of ice. It would lead to different challenges and interactions with Anna, like having to deal with the consequences of changing time to save someone, but also the potential chaos it could cause in Arendelle.
One idea could be exploring Sly's ancestors further. Maybe there are hidden secrets or powers among them that Sly discovers during a new heist. Another could be a time - travel mishap that strands Sly and his gang in an era they've never been to before, like the prehistoric age, and they have to use their skills in a completely different environment.
One idea could be to explore what would happen if the main character accidentally stole a story from a parallel universe. Another could be a time - travel based fanfiction where they go back to the origin of the first stolen story. Or perhaps a story where the characters swap their story - stealing abilities with each other.
One plot idea could be exploring the backstory of the characters in more depth. Maybe show how they became the way they are in the original story. Another idea is to create a different ending, like instead of the traditional happily - ever - after, there could be a bittersweet ending that makes the readers think more. A third plot idea could be to introduce new characters that interact with the existing ones and change the course of the story.
One idea could be a modern Cinderella story where she is a struggling artist instead of a maid. The prince could be a famous art collector who discovers her work at a local gallery. Another could be a Snow White retelling where the seven dwarfs are a group of misfit hackers who protect her from the evil queen's cyber - attacks. And a third could be a Beauty and the Beast story set in a high - tech research facility where the 'beast' is a scientist with a disfiguring accident and 'beauty' is a young intern who helps him regain his confidence and reverse the damage.