Looking for April Fool’s jokes on the Net? Stop reading now if you don’t want them ruined for you. The Washington Post has a rundown of those they’d found as of this morning.
The most prominent is probably the Google Gulp on Google’s homepage, on which someone obviously spent a fair bit of time.
See the Post article for a few others, and this article in the Mississippi Sun-Herald for a history of April Fool’s jokes.
For a pre-Net AFJ, see the New York Times recount of a famous Sports Illustrated article on Sidd Finch, an obscure 168-mph throwing fastballer.
Finally (among the ones I’ve found), you have to be a real physics geek to enjoy this joke by Peter Woit of the blog Not Even Wrong.