It happened to me once while my father was spanking me. I was in 3rd grade.
We had just gotten home from school. It was lunchtime. My father was very angry that day.
I had to pee so bad ! I was about to pee in my pants, I was unable to think to something else. As soon as I put my coat down, I rushed to the bathroom, but my father said I would be punished first. He grabbed me by the arm and took me into the kitchen. I did not expect at all what happened next. To my surprise, my father unbuckled my belt and pulled my pants down, then slid my underpants to my ankles. I was standing there naked, in front of my younger sister and my mother. It was very embarrassing.
When my father started to spank me, I lost control of my bladder and I let a squirt out at each swat. I was dying of shame ! I was afraid to be punished more for peeing, Luckily, my father didn't notice anything. I'm pretty sure my mother and sister saw it, but they didn't say anything.
After the spanking, I just ran to the bathroom. I did even not pull my underpants up, I went through the house completely naked.
A few minutes later, as I sat at the table, I heard my father ask, "Who spilled water in the kitchen?"