Luckily, there's Google (who, btw, had some good ones this year). After looking through a bunch of this year's pranks, I have decided that I like this one best.
Aviary Launches Crane!
By Meowza Katz on April 01, 2009
Aviary is proud to announce that it has launched its newest product, Crane, the web's first paper-based image editor.
For example, to draw in Crane, simply place the Pencil Tool between your index finger and thumb (located on your dominant hand). Press the tip of the Pencil Tool down onto your canvas and using controlled strokes, you will be able to simulate the act of digital drawing on your canvas.
Read the whole hilarious thing here.