This is from Dave Coble and was published on the Groaners listserv.

To conclude the course’s segment on science fiction, the teacher assigned the class a paper on any topic they wished having to do with science fiction. The next week, after the papers had been turned in, the professor was grading them and came across this paper:

There once was an Israeli border guard named Isaac. Across the border from Isaac, Abdul, an Arab border guard, had his post. One night, Abdul crept over the border and killed Isaac.

When Isaac’s commander found out what had transpired the previous night, he was furious, and the next night, he and his squad staged a raid in which several Arab border guards, including Abdul, were killed. This, of course lead to Arab reprisals, which in turn lead to Israeli reprisals, which in turn…ad infinitum. Eventually, the Arabs and Israelis were at war.

Well, the professor read this paper, and being utterly confused, reread it, shook his head in disgust, and wrote a large “F” on it, in red ink, and then moved on to the next paper.

The next day, at the end of class, he handed back the papers, and as he was preparing to leave, the student who received the “F” approached and asked to speak with the professor.

I don’t understand why you didn’t like my paper,” the student said.

“It’s very simple,” the professor replied. “You were assigned to write a paper on science fiction. This paper has nothing whatsoever to do with the assigned subject.”

“I must disagree,” said the student. “I think that my paper examined the very basis of Zion’s Friction.”