We had a few April Fool's jokes on Identi.ca. One year, we launched a few fake social sites like Freelicious and Foursqualour, parodies of existing sites at the time.

Another year, everybody on the network took on new accounts spoofing Twitter celebrities of the time. It is one of my fondest memories of the network.

On Wikitravel, we created a travel guide to the fictional island of San Serriffe one year. It was a lot of fun.

https://wikitravel.org/en/San_Serriffe