I remember when I was 15 and got my first stereo, it was a Pioneer system with 200 watts per channel. I had some helluva headphones and was cranking it up loud one night with some Black Sabbath, but didn't realize they were not plugged in all the way - so I could hear it through the headphones, but the speakers were playing too.
OMG, my dad came crashing through my bedroom door, I yanked off the headphones, heard the speakers blasting Black Sabbath and was thinking 'oh ****, what have I done'... needless to say, I got restricted from my stereo for a week!
BTW, my dad was a preacher, so he was unimpressed with my choice of music