One interesting plot twist could be that Ladybug, while in a fight, is magically transported to the Mulan universe. There, she has to learn Mulan's way of fighting to get back home. Maybe she teams up with Mulan herself against a common enemy like an akumatized Shan Yu.
One plot twist could be that Hawk Moth teams up with Jafar. They both have their own evil plans, and together they become a more powerful force. Ladybug and Cat Noir then have to rely on Aladdin and Jasmine's knowledge of Agrabah to find a way to defeat them. Another twist could be that the Miraculous jewels are actually ancient artifacts from Agrabah that were lost long ago, and Aladdin accidentally stumbles upon one, which draws Ladybug and Cat Noir to his world.
An interesting twist could be that the hypnosis isn't just a simple mind - control. Instead, it's a form of time - travel hypnosis. The characters are hypnotized and sent back in time to when Hawk Moth first got his powers. They then have to figure out a way to stop him from getting the powers in the first place, all while dealing with the disorientation of being in a different time period and the limitations of their Miraculous in the past.
Well, in some fanfictions, a really cool plot twist is when Ladybug's identity is revealed during a moment of extreme danger. For example, she's about to be defeated by a powerful villain, and in a desperate move, she reveals herself to get help from a particular character. And sometimes, the identity is revealed not just to one person but to a whole group, and they all have different reactions. Some might want to protect her even more, while others might be jealous or scared of the power she holds.
Another plot twist could be that the thief has a connection to the Miraculous themselves. Perhaps they are stealing Miraculous - related items in order to create a new, more powerful Miraculous. This would put them in direct conflict with Ladybug and Chat Noir, who are sworn to protect the Miraculous.
Well, in some fanfictions, a plot twist might be that there's a third party who already knew their identities all along and has been manipulating events. This third party could be using their knowledge to either bring them closer or drive them apart for their own motives. Also, there could be a plot twist where the big reveal is actually a false one, set up by Hawk Moth to deceive them and gain an advantage in his fight against the heroes.
One interesting plot twist could be that instead of Hawk Moth being the main villain, it's someone from the Swan Lake story who has been corrupted by dark magic. For example, Rothbart could be working with Hawk Moth to create more chaos. Another twist might be that Ladybug and Chat Noir get trapped in the world of Swan Lake and have to find a way to break the curse there in order to return to Paris and continue fighting akumas.
Well, sometimes in fanfiction, a plot twist is that Ladybug turns out to have a hidden power that is related to being unmasked. For example, she might be able to create an illusion of her unmasked self to deceive the villains. And in some stories, Chat Noir is unmasked first and it causes a huge rift in his relationship with Ladybug because she feels he was careless. This then leads to a whole new set of challenges for them to overcome.
One common plot twist could be that a character who seems like an ordinary human in the Miraculous Ladybug world is actually a werewolf in disguise. For example, perhaps someone close to Ladybug or Chat Noir is secretly a werewolf, and this is only revealed when there's a full moon during a crucial battle. Another plot twist might be that the Miraculous themselves have some sort of connection to the werewolf curse. Maybe the powers of the Miraculous can either control or be affected by the werewolf transformation. Also, a plot twist could involve a werewolf being the key to solving a major problem in Paris that Ladybug and Chat Noir have been struggling with, like a supervillain who is using the werewolf's power for evil and the werewolf has to team up with the heroes to stop it.
One common plot twist could be a character turning out to be a secret villain at the summer camp. For example, someone who seemed really friendly and helpful at first might be revealed to be working for Hawk Moth. Another plot twist could be a mix - up with the Miraculous. Maybe two characters accidentally swap their Miraculous and have to figure out how to use the new powers while keeping it a secret from the others at the camp. Also, there could be a plot twist where the location of the summer camp is actually a strategic place for Hawk Moth's next big plan, and the heroes have to discover this before it's too late.
One idea could be a story where the Peacock Miraculous has a unique malfunction that causes it to create unexpected akumas. For example, instead of creating the usual villains, it creates akumas that have the power to spread positive emotions but in a chaotic way that still disrupts Paris. Another idea is a fanfiction where the holder of the Peacock Miraculous has to team up with Ladybug and Chat Noir to fight against an ancient evil that is specifically drawn to the power of the Peacock. This could involve exploring the history of the Miraculous and its connection to this new threat.