What if pilot gets his tie stuck on the toilet, copilot tries to help and door slams shut with nobody in command WITH the superdoor?
If the guys in front are dumb nuff to do that, they will not ever get to the front seats of anything other a C-172 & that will kill them within 100 hours o f flight time… ie, it ain’t gonna happen. 
Most likely possibility would be bad food, but that wouldn’t be likely to kill anyone. Or how about some kind of venomous cold blooded animal is on the flight deck and bites both of them.
We have procedures to avoid dual food poisoning but I don’t know that it would be that effective. We can’t have the same food as each other and/or we have to eat 30 mins apart.
The door can only be locked from the inside.
I did not know about the door being only locked from inside. You learned me something. LOL
Is there any reason that it is permissible for both pilots to leave the flight deck at the same time?
Snakes on a plane?
Pff. Like that would ever happen. :rolleyes: