British Broadcasting Corporation, 1965
The BBC has a long and distinguished history of April Fools' Day shenanigans. According to The Times of London, the British media company has broadcast fake reports on everything from Swiss spaghetti trees to temporarily weakened gravity.
But the BBC's coup de grace may have come when it told viewers it had perfected Smellovision, which could transmit scent via ordinary TVs. Several viewers were convinced they could smell the chopped onions from the broadcast - no small feat for a technology that didn't exist.