Okay, silly story from a lollipop special... nothing to do with aviation except it took place on a PIA 747, because the VC-10s had been retired.
My brother and I announced that we had psychic powers. He would lay out four playing cards, I would turn my back, one of the other "diplobrats" would point at one, my brother would tell me to turn round, I'd make a huge show of "guessing" which card had been pointed at, and then identify it.
Worked every time.
They couldn't work it out.
Eventually they forbade my brother from speaking to me, but by this time they were so engrossed with the cards that I was able to simply look over my shoulder during the pointing phase - and nobody noticed.
And after that one we said that we were exhausted, all this psychic stuff was hard work, and so on.
The trick was *very* simple. "Okay" or "Ready" - first card. "Turn round now" - third. "Yes, done" - second.