Got this joke from my wife who got it from a friend:

A young engineer who graduated with distinction, was leaving the office at 3.45 p.m. when he found the Acting CEO standing in front of a shredder with a piece of paper in his hand.
"Listen," said the Acting CEO, "this is a very sensitive and important document, and my secretary is not here. Can you make this thing work?"
"Certainly," said the young engineer. He turned the machine on, inserted the paper, and pressed the start button. "Excellent, excellent!" said the Acting CEO as his paper disappeared inside the machine, "I just need one copy."
 
Lesson: Never, ever assume that your boss knows what he’s doing.