It might be that they thought your clothes were dirty and they wanted to wash them all at once without you having a chance to object. So they just took them all in one go.
At first, I was in disbelief. Then I started to feel embarrassed and vulnerable. I probably covered myself up as best as I could and tried to find something to wear while asking them what on earth they were thinking. I would also be thinking about how this could have been avoided if they had just talked to me first.
It might be part of a creative play. For example, if they were acting out a story or a scene from a fairy tale where mom was playing a character that needed to be on the 'lap - horse' or something similar. This kind of play helps in strengthening the family relationship and creating shared memories.
Perhaps it was a situation where there was a costume party in the neighborhood and the neighbor mom was wearing a 'nude - colored' body - suit that made it look like she was nude at first glance. When people realized it was just a costume, it became a funny story. Another possibility is that in a play or theater production in the neighborhood, the neighbor mom was playing a role that required her to be in a state of 'apparent nudity' for artistic purposes, but it was all within the context of the performance.
One reason could be that she was too engaged in the party activities. For example, if she was playing some active party games, her clothes might have come off accidentally. Another reason could be that the clothes were not fastened properly. Maybe the zipper was loose or the buttons were not done up all the way.
One possible reason could be for medical treatment, like if she had to undergo chemotherapy. Chemotherapy often causes hair loss, and some people choose to shave their heads preemptively.
Maybe the story is about a family that values creativity and self - expression. The mom might see making her son wear girls' clothes as a form of art or a way for him to explore different identities. Another possibility is that it's part of a plot to show the son's journey of acceptance in a community that has different views on gender.
Maybe she was trying to share a nostalgic memory. For example, she might have been reminiscing about a special occasion when she wore a particular lingerie piece, like her wedding day. It could also be a way to bond with you, showing a more personal side of herself.
One reason could be that you had some sort of physical problem. Maybe you had a minor injury that made it difficult to get to the toilet in time.
Perhaps you didn't do your homework or chores as you were supposed to. Moms usually want their children to be responsible, and when they aren't, a spanking might be seen as a form of correction. For example, if you repeatedly ignored your mom's requests to clean your room, she might have resorted to spanking to get you to understand the importance of following instructions.
It could be a magical or supernatural situation in the story. For example, a spell was cast on her that made her gradually get smaller, and as a result, she shrank out of her clothes. There could also be some sort of scientific experiment gone wrong. If she was exposed to some strange radiation or chemical substance in the story, it might have altered her body size, leading to her shrinking out of her clothes.