I am always terrible at thinking of ways to play jokes on my community on April Fools' Day, so I don't tend to bother. It is always fun seeing the ideas that others come up with, though.
I never played jokes on my websites but I did play a joke on Facebook a few years ago, and said I was done working on my Sonic related projects and released a disassembly to the public that wasn't finished, but of course it was a joke. 😛 I know one of the Admins on Sonic Retro used to add April Fools jokes to the forums but he hasn't done that in years. The last one was a Emerald Hunt where you'd find random Chaos Emeralds around the forum and there was a counter. Plus the banner changed and instead of saying "Sonic Retro" it said "Knuckles' Emerald Hunt". I loved it lol.
I do try to play a somewhat good one on my Hiking with Shawn audience each year.
This past one, I shared a video of a bear I claimed I saw in the local forest (we don't have bears) and told the viewers that the forest service was trying to keep me quiet about it.