In a more metaphorical sense, it might represent a character's sudden realization of having more masculine qualities or power. For example, she could be waking up to a newfound assertiveness or a sense of being in a male - dominated world where she has to adapt to male - like characteristics to survive or succeed.
There would likely be shock and confusion. People around her would be at a loss for how to handle such a situation. Her family and friends might initially be in denial, thinking it's some sort of prank or a medical misdiagnosis.
It could be really confusing and overwhelming. He'd have to deal with all the societal expectations and differences that come with being a girl.
One possible reason could be self - defense. If the boy was harassing or threatening her in some way, she might react instinctively to protect herself. For example, if he was making inappropriate advances, kicking him in the balls would be a way to stop him immediately.
Perhaps in a school debate. There's a girl who is very intelligent and well - prepared. A boy tries to undermine her during the debate with some snide remarks. But she comes back with such strong arguments and facts that she completely embarrasses him. It's like she 'busts his balls' in terms of his ego and his attempt to put her down in the intellectual arena.
It could be due to some sort of psychological trauma. Perhaps X 23 witnessed something extremely terrifying or disturbing in Westeros that the mind just couldn't handle, so it blocked out all memories as a defense mechanism. For example, seeing a dragon up close in a very violent situation could be too much for the mind to process.
Well, it could be about a magical spell. Maybe he offended a witch and she turned him into a girl as a punishment. He then has to go through his day trying to figure out how to reverse it while dealing with all the new experiences of being female, like wearing different clothes and having different social interactions.
Maybe he was involved in some rough sports. For example, in a game like rugby where there is a lot of physical contact, a wrong move could lead to such an accident.
One possible reason could be a shipwreck. If she was on a boat that sank, she might have lost her clothes during the chaos and been washed ashore. Another reason could be that she was a victim of some sort of natural disaster like a flood that carried her away from her home and belongings.
This could be part of a prank in the story. Maybe the girl is trying to get back at the boy for something he did, like playing a mean joke on her. So she decides to embarrass him by tying him up and putting him in girl diapers as a form of revenge.
One reason could be for a performance like in a play or a movie. Just like I mentioned before, if there is a shortage of female actors, a boy may have to step in. Another reason could be for a prank among friends, just for fun. For example, to surprise their friends at a party by showing up dressed as a girl.