999: The world's oldest emergency services phone number(independent.co.uk)

  Among his other activities, Woz collects phone numbers, and his
  longtime goal has been to acquire a number with seven matching digits.
  But for most of Woz's life there were no Silicon Valley exchanges with
  three matching digits, so Woz had to be satisfied with numbers like
  221-1111. Then, one day, while eavesdropping on cell phone calls, Woz
  begin hearing a new exchange: 888. And then, after more months of
  scheming and waiting, he had it: 888-8888. This was his new cell-phone
  number, and his greatest philonumerical triumph.
  
  The number proved unusable. It received more than a hundred wrong
  numbers a day. Given that the number is virtually impossible to
  misdial, this traffic was baffling. More strange still, there was
  never anybody talking on the other end of the line. Just silence. Or,
  not silence really, but dead air, sometimes with the sound of a
  television in the background, or somebody talking softly in English or
  Spanish, or bizarre gurgling noises. Woz listened intently.
  
  Then, one day, with the phone pressed to his ear, Woz heard a woman
  say, at a distance, "Hey, what are you doing with that?" The receiver
  was snatched up and slammed down. Suddenly, it all made sense: the
  hundreds of calls, the dead air, the gurgling sounds. Babies. They
  were picking up the receiver and pressing a button at the bottom of
  the handset. Again and again. It made a noise: "Beep beep beep beep
  beep beep beep."
  
  The children of America were making their first prank call.
  
  And the person who answered the phone was Woz.