"Who sneezed?"
Noone answers. Stalin orders the guards to escort the last three rows of people outside, where they are executed. Stalin then asks,
"Now, who sneezed?"
Again, noone answers. Again, Stalin orders the guards to escort the last three rows outside. Shots are heard. Again, Stalin asks,
"Now! Who sneezed??"
A small, bespectacled man in the second row raises his hand and says,
"Um, I did, comrade."
To which Stalin replies,
"Bless you."
... and then continues his speech.