Looks like the Conficker computer worm will turn out to be the largest hoax in April Fool?s Day history. Let's see the first television hoax on April 1st of 1957.
The BBC?s report on the spaghetti harvest in Switzerland, on April 1, 1957.
This is believed to be one of the first times the medium of television has been used to stage an April Fools Day hoax.
The origins of April Fools Day are not clear but it is known that the tradition of practical joking and mischief-making dates back to Ancient Roman times. It appears that the festival is closely related to the coming of Spring. Ancient Romans and Celts celebrated a festival of practical joking at about the time of the Vernal Equinox, as do millions of India's Hindus.
The French also mark 1 April but instead of April Fools they call it Poisson d'Avril (April Fish). Source -BBC