I did this unintentionally in college once by switching the keyboard layout to Dvorak, which for some reason persisted across logins. I came back later that day to the same lab and the station I had been using was marked "Out of Order". Huh, that's weird. Sat down at the station next to it. Next day both of them were marked "Out of Order". Oh, huh. Is there something weird with the keyboard? I might know what happened...