OCAU has a tradition of posting April Fools jokes on the news page shortly after midnight on April 1st. These usually take the form of dramatic policy change announcements, which often provoke an irate response from people who don't realise it's a joke.
Here's the pranks from the past:
2012: Two different news pages would load randomly for people. Page A said "no more misc pics due to legal issues" and Page B said "no more tech news, only misc pics from now on". They both linked to the same comments thread, with confusing results.
2011: Facebook logos and info boxes were added to the news page, and people were informed that they would soon need to have a Facebook account in order to keep using OCAU.
2010: A range of new OCAU merchandise was announced, with some unexpected items.
2007: OCAU's front page was blank except for the message "sauce code hacked by mmx bandits". Visitors were then immediately redirected to a random page about cats or kittens.
2006: Back to the Good Old Days! - many forums to be deleted, no more new members, forum accounts under 2 years old to be deleted.
2005: Agg was away at World Superbikes, so no official prank, but Mred32 had a weird problem with the news page which confused a few people anyway. :)
2004: Become an OCAU Subscriber! - OCAU announces plans to charge outrageously for access.
2003: Moving on.. - Agg sells OCAU to TweakTown, so he can pursue his dream of writing a romance novel. TweakTown was in on the action, and announced it had been sold to OCAU.