I think my vote for the best April Fools Joke of all time goes to the BBC in 1957. I hadn't seen it since I was a kid. This may have been the first time that the medium of Television was used to play such a joke. But it certainly isn't the last. (watch)
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 would appear 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.
Since 2001, the United States has celebrated April Fools day everyday.
(illustration courtesy of Tom Richmond)