Here is a list of April Fool's Day jokes/pranks pulled:
Tower of Pisa: The Dutch television news reported once in the 1950s that the Tower of Pisa had fallen over. Many shocked people contacted the station.
In 2008, the BBC reported on a newly discovered colony of flying penguins. An elaborate video segment was even produced, featuring Terry Jones (of Monty Python fame) walking with the penguins in Antarctica, and following their flight to the Amazon rainforest.
Dead fairy hoax: In 2007, an illusion designer for magicians posted on his website some images illustrating the corpse of an unknown eight-inch creation, which was claimed to be the mummified remains of a fairy. He later sold the fairy on eBay for £280.
Water on Mars: In 2005 a news story was posted on the official NASA website purporting to have pictures of water on Mars. The picture actually was just a picture of a glass of water on a Mars Candy Bar.