.. when you are doing something or are at a certain time or place. It can be "mean" comments or things that were not supposed to be said in a situation. like that-
This game gives you a certain situation and the next poster gives an answer and presents another situation.
Here's an example:

Things you shouldn't say when you are on an airplane...
"Is it normal when only one wing is in flames?"
or
"Could you lend me your barf bag, please. I will need more than one for sure."
or
"Can you believe you can get explosives on board in your shoes? Look..."

So: Things you shouldn't say when you're in a movie theater.