As the subway train emerged from the tunnel, the conductor saw there were only 7 people aboard. "Ring the bell for all above- ground stops," he announced over the speaker, knowing he wouldn't need to stop at all 18 above ground stops.
Little Johnny rang the bell before the first stop.
The doors opened.
Nobody got out.
The doors closed and the train went on its way.
Just before the second stop, Little Johnny rang the bell again.
Again the doors opened.
Again nobody got out.
Again the doors closed and the train went on its way.
This process was repeated for fifteen more stops, with Little Johnny ringing the bell every time, the doors opening but nobody getting off the train.
When the train arrived at the last stop and the doors opened, all seven people got off.
The conductor yelled over to Little Johnny. "Hey! How come you kept ringing the bell when you didn't need to get off the train?"
"I did just what you told me to do," Little Johnny replied. "You said, 'Ring the bell for all above ground stops!'"