Perhaps in a world where there is a spiritual connection between humans and monsters. A human who has always been drawn to Nergigante, through intense meditation and connection with the monster's essence, gradually undergoes a transformation. This transformation is not just physical but also mental, as the human starts to think like Nergigante, seeing the world as a place of hunt and survival.
One way to develop it could be through a magical encounter. Maybe the human stumbles upon an ancient relic in a forgotten cave. This relic releases a strange energy that slowly starts to transform the human into Nergigante. As the transformation progresses, the human begins to experience new instincts and powers related to the fearsome beast.
The human - turned - Nergigante discovers that they can communicate with other Nergigantes in a way no human ever could. However, they find out that the Nergigantes are planning an attack on a human settlement. This creates a moral dilemma for the transformed human. Do they side with their new kind or try to protect their former species?
The story could also explore the reactions of the animal kingdom to this strange adoption. Other lions might be confused or even hostile towards the lioness for taking in a human. Meanwhile, the human community might be in shock when they discover the child is being raised by a lioness. They would have to decide whether to try and rescue the child or let nature take its course.
One way the story could develop is that Mariep Dean wakes up one day to find herself in a girl's body. She then has to navigate a world that now treats her differently. For example, she might face new social expectations at school or in her community. She could struggle with how to interact with her friends who now see her as a girl.
I'm not sure about specific 'female nergigante x human' fanfics. You could try searching on some popular fanfic platforms like Archive of Our Own. They have a large collection of fanfictions from various fandoms and might have what you're looking for.
First, establish the character of the human before the transformation. Show their normal life, their relationships, and their goals. Then, introduce the event that causes the transformation into a time baby. It could be a magical spell, a scientific mishap, or a strange encounter. Next, explore the new abilities and limitations of the time baby. For example, they might be able to travel through time but be unable to communicate clearly. As the story progresses, have the time baby face challenges related to their new form and the time - traveling aspect. They could be trying to find a way to reverse the transformation or using their new powers to save someone or something. Finally, conclude the story with either a successful return to human form or an acceptance of the new time - baby existence and a new purpose in life.
Well, the plot could start with a young mechanic who is always around cars. One day, while working on a very special vintage car, there's a strange energy surge. The next thing he knows, he is the car. He experiences life from a different perspective. He can't speak in the traditional sense but tries to convey messages through his headlights and horn. He discovers he has new senses, like being able to detect mechanical problems in other cars just by being near them. He goes on a journey to find a way to turn back into a human while having many encounters with different people and cars along the way.
Maybe in the fanfiction, there's a scientific experiment gone wrong. A human scientist was trying to find a way to bridge the gap between humans and monsters. Sans, being a curious skeleton, volunteered to be a part of the experiment. However, instead of just creating a connection, the experiment transforms Sans into a human. As a human, he experiences new emotions more intensely, like hunger and fatigue, which he didn't really have as a skeleton. He then uses his new human form to try and convince other humans that monsters are not to be feared.
Pikachu might find it difficult to communicate at first. Since it was used to making 'Pika - pika' sounds, it would have to learn human languages. It could start with simple words and phrases, and as it becomes more proficient, be able to have complex conversations. For example, it might try to explain to Ash how strange it feels to have fingers instead of paws.
One possible plot could be Sonic accidentally getting hit by a strange energy beam during a battle with Dr. Eggman. This beam could have some sort of mutagenic effect that slowly starts to transform him into a human. As he turns into a human, he has to deal with the loss of his super speed at first. He then has to adapt to living as a human while still trying to protect his friends and the world from Eggman's new threats.
One way a human could 'turn into' Zelda fanfiction is through creative writing. If a person is deeply inspired by the Zelda universe, they can start by imagining themselves as a character within it. For example, they could write about waking up in Hyrule, with all its unique landscapes and creatures. They might describe their experiences, like facing off against Bokoblins or exploring ancient dungeons. By using vivid details and elements from the Zelda games, they can create a fanfiction that is centered around their 'human' self in the Zelda world.