I may or may not have hid the truth about this in the past, but I did in fact crap my pants while running once. I believe it happened when I was 16, though I do not recall exactly, and most of the details escape me at this point.
I think I was out for a 2 or 4 mile jaunt around the neighborhood, because all my runs back then consisted of one or two circuits around the same 2 mile loop. As was normal for me back then, I was trying to go as fast as I possibly could that day. I was having some problems, but felt like I could hold it. Then, somewhere around a half mile from home, I suddenly lost control and it happened. How embarrassing. Thankfully, it was after dark and I was able to dispose of my soiled clothing shortly thereafter. Oh well, it happens.