"Bill Cosby" joke

One day the teacher walks into her classroom and announces to the class
that on each Friday she will ask a question to the class and anyone who
answers correctly doesn't have to go to school the following Monday.
On the first Friday the teacher asks: "
How many grains of sand are on the
beach?"
needless to say, no one could answer.
The following Friday, the teacher asks the class: "
How many stars are in
the sky?"
and again no one could answer. Frustrated little Johnny decides
that the next Friday he would somehow answer the question and get a 3 day
weekend.
So Thursday night Johnny takes 2 ping pong balls and paints them black.
The next day he brings them to school in a paper bag. At the end of the
day just when the teacher says, "
here's this week's question,"
Johnny
empties the bag to the floor sending the ping pong balls rolling to the
front of the room. Because they are young kids who find any disruption of
class amusing, the entire class starts laughing.
The teacher says, "
ok, who's the comedian with the black balls?"
Immediately, little Johnny stands up and says, "
Bill Cosby, see ya on Tuesday!"