One reason could be that the pants are too big. If she borrowed someone else's pants or bought the wrong size, they might not fit properly around her waist and could easily fall down, just like in the case of the girl at the carnival.
Well, sometimes the lack of proper undergarments can contribute. If she doesn't have a belt or the right kind of elastic in her underwear, it might not hold the pants up well. Also, if she has been wearing the pants for a long time and they have stretched out, they could fall down. And in some comical stories, there could be some external factor like another person accidentally pulling on them in a chaotic situation.
Faulty clothing items can also be the cause. For example, a broken zipper or a loose button. In the story of the girl in the school play, the faulty zipper led to her pants falling down. Another reason could be sudden and extreme movement. When a girl runs really fast or makes a very quick turn like the girl in the park, the momentum can cause the pants to slip down if they are not very secure.
In some cases, she could have been given a lot to drink without realizing how quickly it would affect her. For example, if she was at a party and drank a large amount of liquid very quickly. Or she might have been wearing clothes that were difficult to take off quickly in case of an emergency, which contributed to the accident.
It might be due to a lack of access to a toilet in time. She could have been in a situation where there were no bathrooms around, like being in a long line outside a public restroom and not being able to hold it any longer.
Nervousness could be a reason. Just like in the case of a girl giving a speech or performing on stage, she might be so focused on not messing up that she forgets about her bladder.
Maybe she was playing too hard and ignored the urge to go to the toilet for a long time. Kids often get so engrossed in their play that they forget about their bodily needs until it's too late. Also, it could be that there was some kind of problem with the toilets around her. For instance, if all the nearby public toilets were locked or out of order and she couldn't hold it any longer.
Well, in a story, it could be that she got scared suddenly. Fear can sometimes make it hard to control one's bladder. Or perhaps she was ill and her body couldn't hold it as normal. Maybe she was in a hurry and thought she could hold it until she reached a bathroom but miscalculated. Like if she was running to catch a bus and thought she could make it but then peed her pants on the way.
There could be a situation where the girl was at a dance party. She was doing some wild and energetic dance moves. Her pants were a trendy but not very well - fitting pair. With all the twirling and jumping, the pants slipped down and fell off. At first, she was mortified, but the other party - goers were very kind. They cheered her up, and one of the girls lent her a long shirt to tie around her waist as a makeshift skirt until she could get home to change.
Well, she might be a very young girl who hasn't fully developed the ability to control her bladder yet. Also, she could be in a situation where there was no easy access to a toilet, like being outdoors in a park far from the restrooms. Sometimes, fear can also play a role. For example, if she was in a new place and was afraid of using the strange - looking toilet, she might end up peeing in her diaper instead.
Medical issues could also be a factor. Maybe she has a small bladder or some sort of urinary tract problem that makes it difficult for her to hold her pee for long periods. Also, if she has been drinking a large amount of fluids in a short time without realizing it, it can lead to this situation.
One reason could be the saturation of the market. There are so many Naruto fanfictions out there that it's hard for new ones to stand out. Another factor might be the decline in the overall popularity of the Naruto franchise over time, leading to less interest in its fan - created content.
Well, sometimes a girl might poop in her pants because she was too engrossed in an activity. Let's say she was playing a really exciting game outside and didn't want to stop to go to the bathroom. Also, not having access to a toilet in time can be a cause. If she's in a situation where there are no toilets around, like in the middle of a long hike, she might end up having an accident.