I submitted this story to DailyWTF last year. They published it, but for some reason, rewrote it (badly).
Here is the original (true) story...
In the late 80's, I was lead developer for a large hotel chain. We had 240 hotels running off of 4 big regional minicomputers. Each mini handled 60 or so hotels dedicating 6 ports for terminals, printers, etc. This pushed the hardware we were using considerably, causing occasional system 'burps', bumping all the ports numbers over by one. The front desk staff would see bizarre things such as print jobs dumping to their terminals, and the main menu printing out on the printer.
Each mini also had a single port dedicated to developer dial-in support. In the age of 2400 baud modems, security and hacking were tame issues, met by equally tame preventative measures.
Anyone accidentally stumbling upon the dial-in number would see a typical login page. Enter anything but a secret code of the day, and the would be hacker would be left pondering a message that their break-in had been detected, the line had been traced, and the police were being contacted... It was all fake, but we figured what the hell, try to scare em off.
One day, after a one of those system 'burps', a bizarre support call was received at corporate support. A front desk clerk at one hotel was on the line frantically exclaiming "Help! the computer is calling the police!"