Did it the first time I got stuck and spun tyres in a car. Was only around 13 and been driving around the farm we live at. I was just driving and sliding the car about, but ground was really wet, and I tried getting up a steep slope, but the wheels kept spinning. Next thing I knew, I was hard as a rock, and before I could get it out, I shot a load, half in my pants, and half down my jeans. Was the first time I found out spinning in mud gets me horny !