I use Answerbag.com, and I plan to ask obvious and superfluous questions that day, questions everyone already knows the answer to, and just random, silly questions.
I can't think of what to do on Wrongplanet, so I guess I'll just be business as usual here.
As for offline, I doubt I'll do anything that has to do with April Fools day. If I go to church next morning, they might have something related to April Fools, who knows what it'll be though unless I get to see it for myself.
So users, what do you plan to do for April Fools on Wrong Planet? On any other Website (mention them, please)? Offline?