This reminds me of the day I went to sign up for the RAF. We were all sat rather nervous. The corporal, replete with handlebar moustache, sat at his desk smoking his pipe. The sergeant came down to summon us upstairs to take the oath; meanwhile saying, "Corporal, what the hell are you smoking in that pipe?"
"Three Nuns (a popular pipe tobacco at the time), Sarge."
"Three Nuns? Smells to me as though two of them have sh!t themselves!"
Obviously a set piece which they must have practised often, but it had the effect of making everyone relaxed.