It is an ancient and noble tradition, among certain newspapers, to mark the first day of April by sneaking a fanciful work of fiction into their otherwise reliable pages. One of my favourite examples of the genre is the Guardian's classic 1977 article on the island nation of San Seriffe (comprising the islands of Upper and Lower Caisse, and ruled by the dictatorial General Pica).
But what do you do if you're in the satire business, and such spoof articles are your regular stock in trade? Well, if you're The Onion, what you do is put together an April Fool's Day issue that consists entirely of sober, factual reporting about the real events of the day. It's quite impressive, really—not just as a brilliant meta-prank, but as actual journalism. If The Onion did this every day, we wouldn't need the New York Times.