The Koan
The master took a piece of chalk and drew a line on the floor. He then said to the disciple, "How will you make this line shorter?" After thinking for a while, the disciple said, "I'd rub out a portion of it".
The master shook his head. He then bent down and drew another line, parallel to the first one, but longer.
On seeing this, the disciple grabbed hold of the master and threw him against the wall of the monastery.
The master was enlightened.
Commentary
"I have been your disciple for ten years. I have waited on you hand and foot, have cooked for you, have washed your clothes, have swept the monastery all this time, without a word of complaint. During these ten years, not even once have you condescended to teach me The Way. When you called me to your quarters today, I was ecstatic, thinking that I was finally going to be initiated into the Noble Path. Instead, you ask me to solve a puzzle, a puzzle that legions of people know the answer to, either by virtue of having spent their Saturday afternoons watching B-grade karate flicks or by reading enlightened blogs. At first, I thought I'd be clever and ask you 'Shorter than what?', but decided against it. Who knew, venerated master that you are, maybe you had a trick up your sleeve, after all. But oh no, I was giving you too much credit. Come to think of it, I should have seen the signs when you simply waved your hand disdainfully and said 'Cow' when I asked you about Mu.
"And dude, BTW, do something about your B.O."
(Apologies to Joe Hyams)