Once I was using my father's computer and changed the screen resolution. Whatever I chose wasn't compatible with his monitor, so it just went black - and I panicked and started hitting keys, including Enter. Which meant I accepted the change. He was out of town and I can't really if I was really supposed to be using it.
My solution was to go to school the next day, and write down all the steps from startup to accessing the screen settings and changing the resolution using only the keyboard. I was very proud that this worked, but thinking I had ruined my dad's computer was one of the biggest "oh fuck" moments of my childhood.