http://en.wikipedia.org/wiki/555_%28telephone_number%29 wrote:
<<Telephone numbers with the prefix
555 are widely used for fictitious telephone numbers in North American television shows, films, computer games, and other media. Not all numbers that begin with
555 are fictional—for example,
555-1212 is one of the standard numbers for directory assistance throughout the United States and Canada. In fact, only
555-0100 through
555-0199 are now specifically reserved for fictional use, with the other numbers having been released for actual assignment.
The phone companies began encouraging the producers of television shows and movies to use the
555 prefix for fictional telephone numbers, roughly during the 1960s. One of the earliest uses of a
555 number can be seen in Panic in Year Zero! (1962), with
555-2106. In older television shows from the 1950s or 1960s, "
KLondike 5" or "
KLamath 5" was used, as at the time the telephone exchanges used letters and numbers in phone numbers. More recent works set in this period typically use this convention as well. For example, Dr. Emmett Brown's 1955 phone number in Back to the Future is "
KLondike 5-4385".
Before "
555" or "
KLondike 5" gained broad usage, and before touchtone phones became standard, scriptwriters would sometimes invent fake exchanges starting with words like "QUincy" or "Zebra". The letters "Q" and "Z" were not used on the old dial phones.
555 use is only restricted in North America. Neglecting this fact resulted in a lawsuit in the late 1980s: in his daily The Far Side panel, cartoonist Gary Larson included a graffiti of a
555 number by which prank calls could be made to Satan. When the panel was printed in Australia (where
555 was at the time a standard exchange), the owner of the
555 number became the subject of much harassment, and sued Larson and his syndicate for defamation. The suit was unsuccessful.>>