In some fanfics, a diaper could be used as a plot device to show Naruto's vulnerability. Suppose he gets poisoned by an enemy and temporarily loses his ability to control his body functions. His friends then have to take care of him while he's in this state, wearing a diaper. It can be a way to explore the bonds of friendship and loyalty within the Naruto group.
Some Naruto diaper fanfics might explore an alternate universe where Naruto was raised in a very different way and diapers were a part of his early life. For example, if he was raised by a different clan that had some unique traditions involving diapers as a sign of protection or something similar. This could lead to interesting character development and interactions with the other characters from the Naruto universe.
There might be a fanfiction where Naruto discovers a magical diaper that gives him special powers. For example, the diaper could make him run faster or have stronger jutsu. This kind of story would add a fun and unexpected twist to the Naruto world and could be full of humorous situations as Naruto tries to figure out how to control these new powers.
Most Naruto Shippuden fanfics focus on things like Sasuke and Naruto's relationship, the battles against the Akatsuki, or the growth of the younger ninjas. The idea of 'diaper fanfic' seems very out of place. However, if there are such fanfics, they might be more about creating a comical or extremely alternative view of the characters, but it's not something that would have a typical 'interesting' plotline in the sense of the original Naruto Shippuden story.
One idea could be a time - travel fanfic where Naruto travels back in time to when he was a baby. He has to deal with being in diapers again while also trying to use his knowledge from the future to help his younger self and his family. Another idea is a story where Naruto's friends find an old photo of him as a baby in a diaper and they all have a good laugh about it and then it leads to sharing stories about their own childhoods.
In some stories, a diaper boy could be in a magical world. For example, he might find that his diaper has some special powers. When he wets it, it creates a small puddle that can turn into a portal to a mini - adventure world. There he meets friendly creatures and has all sorts of exciting experiences. It's a fun and imaginative take on the idea of a diaper boy.
One teen diaper story could be about a teen who had to wear a diaper during a long camping trip due to a lack of proper bathroom facilities. Another might be a teen athlete who wore a diaper during a very long endurance event. There could also be a story of a teen with a medical condition that required the use of a diaper for a period of time and how they coped with it at school and in social situations.
One boy diaper story could be about a baby boy who always giggles when his diaper is being changed. His parents find it really cute. Every time they open up the diaper, he starts kicking his little legs and making happy noises.
Well, consider a story of a new mother who was so busy taking care of her newborn that there were times she was so occupied that she used a diaper for herself during those hectic days. It shows how selfless and busy new mothers can be, focusing on the baby's needs first and sometimes sacrificing their own comfort.
One woman diaper story could be about a new mother who found that using a particular brand of diapers for her baby girl made a huge difference. The diapers were super absorbent and had cute designs. It made the whole diaper - changing experience more pleasant as the baby seemed more comfortable and less fussy.
In a diaper kids story, a group of kids at a daycare all have different colored diapers. They start a game where they pretend their diapers are capes. They run around the playground, laughing and having a great time. One of the kids accidentally loses his diaper during the game, which causes a big laugh among the other kids and the daycare workers quickly put a new diaper on him.
One back in diaper story could be about a child who was so excited to start potty training but then had a setback and went back to diapers for a short while. Maybe they were ill and it affected their progress. It was a bit of an adjustment for the family, but they were patient and understanding.