One idea could be that baby Mario and baby Luigi get lost in a magical forest filled with strange creatures. They have to use their baby wits and little jumps to get through obstacles and find their way back home. Maybe they befriend a little fairy who guides them part of the way.
Yoshi is a really popular character to include. He can be like a big brother figure to the baby Mario and baby Luigi. He could carry them around on his back and help them reach high places or cross dangerous areas.
Adventure is also common. They could be on a quest to find a lost item or to explore a new part of their world. It makes for exciting reading as they face various challenges as babies. For instance, they might encounter a small stream that they need to cross but are too small to do so easily. And they have to figure out a solution together. This kind of adventure - based theme is quite popular.
Wart could also be an antagonist. He might try to take over the Mushroom Kingdom where Baby Mario and Baby Peach live. He could send his minions to stop the two from getting help or finding special items that can defeat him.
A really fun 'baby daisy and baby luigi fanfiction' could be set in a world of toys. They are toys themselves and they have to work together to escape from the clutches of an evil toy collector. They make friends with other toys along the way and use their unique skills, like baby Daisy's ability to find hidden paths and baby Luigi's courage, to overcome the challenges.
You can start by focusing on their innocent personalities. For example, show baby Luigi sharing his favorite toy with baby Daisy. This simple act can create a warm feeling in the story.
One popular 'baby Luigi and baby Daisy fanfiction' could be those that focus on their adventures in the Mushroom Kingdom as babies. For example, there might be stories where they discover new power - ups together in a cute and innocent way.
It could be about various things. Maybe it's a fictional story that features Baby Mario and Baby Peach going on adventures together in the Mushroom Kingdom. They might face challenges like dealing with Bowser's minions or finding power - ups.
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.
One idea could be that Baby Mario and Baby Peach go on a magical adventure through the Mushroom Kingdom, encountering new and strange creatures along the way. They might have to work together to solve puzzles to reach a special power - up that can save the kingdom from a new threat.