Maybe there's a new villain in the kingdom who has a device that can transform enemies into harmless forms, like turning Luigi into a baby. The villain wants to use this to stop Luigi and Mario from interfering with his evil plans. Mario has to protect baby Luigi from the villain's minions while looking for a way to break the transformation. This could involve exploring new areas of the kingdom and meeting new characters who might have the knowledge to reverse it.
It could start with Luigi touching an ancient artifact that has the power to age or de - age. Since he doesn't know what it is, he gets turned into a baby. His friends are shocked at first. Mario decides to take Luigi to the local wise old toad who is known for his knowledge of magic. Along the way, they face challenges like crossing rivers and avoiding enemies. Meanwhile, baby Luigi is causing some cute chaos, like getting into mushroom patches and making a mess, but also has an innocent charm that endears him to the other characters.
Mario would definitely be a main character. Since Luigi is his brother, he would be the one most concerned about Luigi's transformation and would do everything he could to help him. Princess Peach could also be a main character. She might offer her castle as a safe place for baby Luigi and use her resources to find a solution. Toad could be there too, helping Mario with taking care of Luigi and providing useful information about the kingdom that could lead to reversing the spell.
In a 'luigi turns into a girl' fanfiction, the plot might involve Luigi being transformed due to a strange experiment gone wrong in the Mushroom Kingdom's science lab. His new female form causes a stir among the inhabitants. He could struggle with how others perceive him now. For example, some characters might treat him differently. However, he also uses this opportunity to see the world from a different perspective and becomes more confident in himself over time.
Well, perhaps the plot could involve Daisy and Luigi facing the challenges of new parenthood. They might struggle to balance their own lives and duties while taking care of the baby. For example, Luigi could be worried about protecting the baby from the various threats in their world, while Daisy is focused on the baby's growth and development.
One possible plot could be that Luigi and Daisy discover they are going to have a baby. They then start preparing their home, like painting a nursery. Luigi might be a bit nervous but also excited, and Daisy could be the strong one, reassuring Luigi throughout the process.
One possible plot could be that the magic backfires on Voldemort during a powerful dark spell. As a baby, he has no memory of his previous self. The wizarding world is in chaos as they don't know what to do with this baby - voldemort. Some might want to kill him immediately, while others think he could be redeemed. Harry Potter, having defeated him once, feels a strange sense of responsibility and wants to make sure he doesn't grow up to be evil again.
Well, one possible plot could be that his friends have to take care of him. They might struggle at first, not knowing how to handle a baby Izuku. For example, Bakugo could be really frustrated but gradually learn to be gentle. Ochaco might be really good at soothing baby Izuku when he cries.
The plot could be that Deku is doing some sort of experiment in the school lab when something goes wrong. A chemical reaction or a malfunctioning device causes him to turn into a baby. All Might hears about it and comes to visit. He feels a sense of responsibility as Deku is his successor. The other students are both amused and worried. They start to learn about taking care of a baby, like feeding, changing diapers, and making sure he sleeps well. Meanwhile, the teachers are researching how to reverse the transformation, and they suspect that it might be related to some ancient quirk theory that they need to dig deeper into.
One possible plot could be that a magic spell gone wrong in Berk turns Hiccup into a baby. Toothless, being his loyal friend, tries to protect the baby Hiccup from the chaos that ensues. The other Vikings are confused at first but then start to take care of the baby Hiccup in their own clumsy ways, leading to some comical situations.
Well, perhaps it could be about a magical event that causes Ash to transform into a baby. Then his friends have to take care of him while also trying to find a way to reverse the transformation. Maybe Pikachu has to protect baby Ash from other Pokémon who might mistake him for an easy target.
Well, it could be that Edward is cursed by a powerful witch. The witch might be angry with him for some reason. And so, he turns into a baby. His friends then have to figure out how to break the curse while taking care of baby Edward. They might go on a journey to find a special herb or a magic item.