I am a Menace to Society

Or at least to society's feet. Lately, it seems like my commute always features at least one episode involving me stepping on someone's foot, doing the quick "Sorry!" while pulling back and smiling apologetically. Just a hazard of commuting by public transportation, to be sure. But yesterday, I managed to knock someone's shoe CLEAN OFF. I have no idea how I did it, or if I could repeat the achievement.