A few years ago, the BBC promoted an upcoming natural history series featuring penguins ... with the remarkable disclosure that these penguins could fly.
Terry Jones showcased the spot, which had persuasive footage of penguins taking flight.
The key detail: it was launched on April the first.
This was not just an April Fool's joke (a long tradition within the BBC, by the way), but one with a purpose: to promote BBC's iPlayer.
They also launched a video to explain the sophistication behind the ruse itself.