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?"

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 two 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, "Okay, who's the comedian with the black balls?"

Immediately, little Johnny stands up and says, "Bill Cosby. See you on Tuesday!"

Scott in Baltimore flipped his wrist and fantasized about truckers
while drooling:
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?"

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 two 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, "Okay, who's the comedian with the black balls?"

Immediately, little Johnny stands up and says, "Bill Cosby. See you on Tuesday!"

That joke is way older than your first experience in a Petro toilet.