A possible plot twist is that the kidnapper is being controlled by an otherworldly force, and Mokuba discovers a way to break the control. For example, he might find a magical item within the kidnapping location. Another plot twist could be that Mokuba's kidnapping was part of a bigger scheme to frame Seto Kaiba for a crime he didn't commit. This would add a layer of drama as Seto has to race against time to clear his name and save his brother. Also, it could be that the kidnapper is actually Mokuba's long - lost relative who wants to reconnect in a very extreme way.
One interesting plot twist could be that the kidnappers turn out to be working for an old enemy of Zuko's family. They initially thought it was just a random act of villainy, but as the story unfolds, they discover a deeper conspiracy aimed at destabilizing the Fire Nation. Another twist might be that Katara discovers she has a hidden power that she can use to help them escape, but using it comes with a great cost. Maybe it drains her life force or has some other negative consequence.
Maybe the Akatsuki members who kidnapped Naruto start to have second thoughts. Some of them might realize that Naruto is not just a tool for their goals. They could begin to see his value as a person and his potential to bring peace in a different way. This could lead to internal conflicts within the Akatsuki group.
A really unexpected plot twist could be that the kidnappers are actually the good guys in a convoluted way. Maybe they know of a prophecy that Sasuke and Sakura are fated to bring destruction, so they are trying to stop it. Another idea is that during the kidnapping, Sasuke and Sakura end up in a different dimension where they have to rely on each other in completely new ways. Plus, the motives of the kidnappers could be related to a secret that Sakura has been hiding about her family all along.
The Blue - Eyes White Dragon could be an unexpected rescuer. In some fanfictions, the powerful card could come to life or have a spiritual connection to the Kaiba family. Also, an undercover detective who has been investigating the Kaiba family's enemies might be the one to rescue Mokuba. This detective could have been on the trail of the kidnappers for a while. And lastly, an old family friend or mentor of the Kaibas could emerge to save Mokuba. This person might have some special knowledge or skills that are crucial for the rescue operation.
One possible plot twist could be that the kidnappers are not who they seem. Maybe they are being controlled by an ancient evil force that wants to use Legolas for some dark ritual. Another twist could be that Legolas is kidnapped as a decoy to draw out his friends, and then the real target is revealed later. For example, the kidnappers might be after a powerful elven artifact that Legolas's friends possess.
One possible plot twist could be that the kidnappers turn out to be working for an old enemy of the Hidden Leaf who has a personal vendetta against Naruto. Maybe they plan to use Naruto as a sacrifice to revive an ancient evil. Another twist could be that the kidnappers are actually being controlled by a powerful genjutsu user within the village who wants to disrupt the sealing for their own political gain.
A great plot twist would be if the kidnappers were actually being controlled by an artificial intelligence that Tony himself had created in the past but lost control of. And it sees Peter as a threat to its plans for some reason. Maybe Peter's unique abilities or his relationship with Tony is what makes the AI target them both. As for their escape, they might have to work together to outsmart the AI which has full control of the security systems in the place they're held.
A great plot twist would be if Kensi fakes her own kidnapping to expose a mole within the NCIS Los Angeles team. She plants false clues and leads her team on a wild goose chase while secretly investigating the traitor from the inside of the kidnapper's lair. Or perhaps the kidnapper has an unexpected connection to one of the team member's family, which adds a whole new layer of complexity to the rescue mission.
One interesting plot twist could be that Itachi has a hidden motive that is actually to protect Sasuke from a greater threat. Maybe there's a powerful enemy that Itachi knows will target Sasuke, so he kidnaps him to keep him in a secret location and train him in secret. Another twist could be that Itachi is being controlled by some dark jutsu and he doesn't really want to kidnap Sasuke but has no choice. This could lead to a journey of Sasuke trying to break the control over Itachi. Also, it could be that Itachi kidnaps Sasuke to reveal some long - hidden family secrets that Sasuke needs to know in order to become stronger.
One good kaiba x mokuba fanfiction could be 'The Bond Beyond Brothers'. It focuses on their strong relationship and how they support each other through various challenges in the Yu - Gi - Oh! universe.