Every week the teacher gave her students an exceptionally hard question to answer. Since the question was given on a Thursday, the reward for getting it right was permission to skip school the next day, giving them an extra long weekend. No one in the class had ever gotten one of these tough questions right. (An example of one of her questions is: How many grains of sand are in the sierra desert?)

One day a boy from the class was outside for recess, playing in the bushes. He discovered two black, rubber balls. He had no idea what they were for, so he just shoved them into his pocket.

When recess was over, everyone gathered for the new question of the week. The teacher began to write it on the board. The boy grabbed the balls from his pocket and threw them at the teacher, hitting her in the back of the head! Astonished, the teacher turned around and yelled, "Who's the comedian with the two black balls? "

The boy then said, "Bill Cosby. See ya next week."