When someone knocks on a locked bathroom door and even worse, turns the knob!
I've had this debate before. What do you answer when someone knocks?
1. Answer in the third person (someone's in here)?
2. Answer as if someone knocked on front door (who's there; der tatte iz nisht in der hoizen)?
3. Noise (cough; flush)?
4. No answer, I'm absolutely sure I locked it, let them try the knob.