One plot twist could be that the 'pregnancy' actually turns out to be a way for Kyuubi to transfer its remaining power to Naruto in a more permanent and extreme way. Instead of just lending power, it's like a total fusion of their essences. Another could be that the 'pregnancy' is a ruse by an enemy who has manipulated Naruto's connection with Kyuubi to make it seem like this is happening, when in fact they are trying to steal the power that would be created from such a union.
In some fanfictions, a plot twist could be that the 'pregnancy' leads to a split in Naruto's personality. Since Kyuubi is such a powerful and chaotic force, as it 'pregnancy - like' state progresses, Naruto starts to exhibit two distinct personalities - his own and a more Kyuubi - influenced one. This internal struggle then becomes the central conflict in the story, with Naruto having to find a way to reconcile these two parts of himself while also dealing with the reactions of his friends and the ninja world around him.
Well, a really interesting plot twist could be that the 'pregnancy' is not what it seems at all. It could be that Kyuubi is actually a reincarnation of an ancient being, and this 'pregnancy' is the key to unlocking the true form of that being, which has major implications for the entire Naruto universe. Or perhaps Naruto's own past life has some connection to this 'pregnancy' situation, and as the story unfolds, we learn that this is all part of a much larger cycle of reincarnation and destiny.
A possible plot twist in a Regina Gets Pregnant Fanfiction could be that the pregnancy progresses at an extremely rapid rate. Instead of the normal nine months, it might be just a few weeks. This would force Regina to quickly adapt to the idea of being a mother and also deal with the physical and emotional changes in a very short time. Additionally, what if the baby is a key to unlocking a long - forgotten magic in the realm? This would make Regina a target for those who want to use the baby's power for their own gain. Or, it could be that Regina's pregnancy is a sign of a new era in the magical world, and she has to figure out how to lead the way into this new future while carrying the baby.
One interesting plot twist could be that the sealing process goes wrong in a completely unexpected way. Maybe instead of just sealing the Kyuubi's chakra, Naruto accidentally fuses with it on a spiritual level, giving him new and uncontrollable powers at first. Another could be that during the sealing, a dark entity from another dimension tries to interfere and take over the Kyuubi's power within Naruto. It would add a whole new layer of conflict and mystery to the fanfiction. Also, perhaps the seal actually has a hidden purpose that was set by an ancient force long ago, and as Naruto discovers bits of this, it changes his understanding of his role as the Kyuubi's host.
Well, there's a fanfiction called 'Kyuubi's True Form'. The plot twist here is that the Kyuubi has a completely different true form than what was expected, and this form has different powers and a different relationship with Naruto. Also, in 'Naruto's Lost Kyuubi', Naruto suddenly loses the Kyuubi for an unexpected reason, like a time - travel accident, and he has to find a way to get it back without his usual power source.
A cool plot twist could be that the pregnancy is a sign of Danny's evolution into a new form. Instead of it being a normal biological pregnancy, it's a supernatural transformation. As he progresses through the 'pregnancy', he gains new powers and abilities that he has to learn to control, and in the end, he emerges as a more powerful version of himself.
One possible plot twist could be that Sebastian's true motives for getting Clary pregnant are revealed to be part of a larger, darker scheme. Maybe he plans to use the baby for some sort of power - play within the Shadowhunter world.
One interesting plot twist could be that the symbiote actually has a mind of its own and tries to take over Naruto completely, but the Kyuubi's chakra interferes and creates an unexpected alliance between the three. This could lead to Naruto having new and strange powers that no one has seen before.
One interesting plot twist could be that in the fanfiction, the fem Naruto in the Kyuubi suit has the ability to communicate with the spirits of past Jinchuriki. This gives her an edge in battles as she can learn from their experiences. Another twist might be that the suit itself has a mind of its own and sometimes takes over to protect Naruto, even if it means going against her own wishes temporarily.
Well, in some 'Naruto corrupted by fem Kyuubi' fanfiction, a great plot twist could be that the fem Kyuubi is actually a part of a larger prophecy that Naruto was unaware of. The corruption she brings is a necessary step in fulfilling this prophecy. It could also be that the fem Kyuubi's true form is not what it seems, and when Naruto discovers this, it completely changes his perception of her and their relationship. For instance, she might be a reincarnation of an ancient and powerful being, and her 'corruption' of Naruto is a way to awaken his latent powers related to that ancient being.
Well, sometimes in such fanfiction, the framing is part of a larger conspiracy. Maybe it's not just about getting Naruto in trouble, but it's a scheme by an enemy village to create chaos within the Leaf Village. They might plant false evidence of Naruto collaborating with the enemy, which then leads to a series of events where Naruto has to prove his innocence while also dealing with the distrust of his friends and the village elders. It can make for a really engaging read as we see Naruto struggle against all these odds.
One interesting plot twist could be that Sherlock initially doesn't believe he's the father and tries to use his deductive skills to disprove it, only to find out he was wrong all along. Another could be that Molly tries to keep the pregnancy a secret from Sherlock at first, but then circumstances force her to reveal it in a very dramatic way, like during a dangerous case. And sometimes, there might be a plot twist where other characters, like Mycroft, try to interfere with the situation for their own reasons, either to protect Sherlock or because of some secret agenda they have regarding the potential child.