What is the world's most best April Fool's joke ever?

Internet to close for cleaning (April 1997)
An e-mail warned users around the world that the Internet would be closed down for cleaning for twenty-four hours from March 31st until April 2nd in order to clear out the "electronic flotsam and jetsam" that had built up on the web, with the cleaning carried out by Internet-crawling robots. (In a previous version of this joke, telephone customers were warned the phone network would be cleaned on April 1st, and were advised to cover their phone with plastic bags to catch any dust which might be blown out during the process(!)

Both of those are good, BUT: I tend to stick with the original; moving New Year's Day to January First.