I'm not really an April Fool's person. Back in High School, there were lots of people who didn't get what a good prank was (e.g. if you told them you'd seen through their jokes, they kept pestering and insisted that it wasn't one, until you finally gave in to shut them up), so I pretty quickly decided that if I did April Fool's jokes it would have to be good ones. And you know how rare those are...
Anyway, Chuq really gets it, it appears, and here's one of his really good and subtle USENET pranks.