A childhood belief about hair

When we were kids, my older sister and I would take our bath together. And our favorite game was to "shave" foam off our backs with our dad's razor, the cap on obviously. But once, I used the razor on my arm without the cap. So as to prevent me from doing it again, my sister told me that I would turn into a very hairy monster. She even convinced me that horns were growing as she was speaking to me, I could feel them!
I called my mother for help, asking her to tell my sister that it wasn't true but my mum confirmed my sister's theory... The following night, I stayed awake, waiting for my body to transform into a beast.