Well, a plot could involve Merlin being undercover as a new student who is actually there to protect the school from a dark magical force that only he can sense. He might have to form an unlikely alliance with the school outcast who turns out to have some latent magical ability. Or he could be in a situation where he has to participate in a school magic competition while hiding his true power level.
One idea could be Merlin as the new student with mysterious powers. He tries to hide his magic from everyone, but it keeps getting him into trouble, like accidentally making things levitate in class. Another could be a high school version of the Arthur - Merlin relationship, where Arthur is the popular jock and Merlin is the nerdy outcast, but they become friends over time.
A plot could revolve around a time - traveling aspect in Lego City Undercover fanfiction. The protagonist accidentally activates a time - traveling device and ends up in the past of Lego City. They have to find a way to get back to their own time while also making sure not to change the past in a way that would destroy the future of the city. This would involve a lot of exploration of Lego City's history and its evolution over time.
One plot idea could be that Ziva and Tony are undercover as a married couple at a high - society event. They have to blend in and gather intel on a criminal who is using the event to launder money. Another could be that they are undercover in a dangerous cult to rescue a kidnapped agent, and during their time there, they start to realize new things about each other. A third idea is that they go undercover as rival spies in an international arms deal, but their fake rivalry starts to turn into something more real and they have to deal with their feelings while still completing the mission.
One plot idea could be Merlin and Nimue teaming up to save a magical forest that is being threatened by dark forces. They could use their combined magic to fend off the evil entities. Another idea is a time - travel plot where they are sent to the future and have to adapt to the new world while also finding a way back. And perhaps a plot where they are wrongly accused of a crime in Camelot and have to prove their innocence together.
One idea could be Merlin having to deal with the political intrigue of being a king. He might face challenges from nobles who don't trust his magic. Another could be Merlin using his magic in unique ways to improve the kingdom, like creating new irrigation systems for farmers. Or perhaps he has to form alliances with other kingdoms while hiding his true identity as a powerful sorcerer.
One idea could be that Merlin, as a wizard, is hunted by vampires because his magic is seen as a threat to their existence. But then he discovers that some vampires are not as evil as he thought and they form an uneasy alliance to fight a common enemy, like a dark sorcerer.
One idea could be exploring a different magical realm within the 'the merlin conspiracy' universe. Maybe there's a hidden land where the magic is more primal and ancient. Another could be a story about a young wizard who discovers they have a unique connection to Merlin himself and must use that to stop a new dark threat.
A plot could involve Merlin getting cursed and the knights having to find a way to break it without Merlin's magic to guide them. They might have to rely on old legends and their own wits to save him. This could lead to some great character development for the knights as they face challenges they usually rely on Merlin to solve.
One plot idea could be Merlin, as a borrower, is discovered by Arthur. At first, Arthur is shocked but then becomes intrigued. He decides to protect Merlin from the other humans in the castle. Another idea is that Merlin, in his tiny form, uses his magic in new and creative ways to help the borrowers' community. For example, he could create miniature tools or defenses against predators. A third idea might be that Merlin has to go on a quest to find a magical item that can restore his normal size, all while facing the challenges of being so small in a big world.
One idea could be that the undercover professor has a secret mission to protect a special student. Maybe the student has a unique power or knowledge that dangerous forces are after. Another could be that the professor is actually from a rival academy, undercover to steal some important teaching methods.