It was December 3, 1976, when Pink Floyd went to Battersea Power Station in London to shoot the cover art for their album Animals. As expected, a 40-foot pink pig balloon was filled with helium, but they weren't expecting the balloon to get away from them and fly over the streets of London. Because of the mishap, aviation officials had to notify airplanes in the area to be on the lookout for the flying pig, and after it landed in a field (scaring the cattle), they returned the following day to shoot again.

The video below shows a recreation of the event, and you'll hear the story straight from the photographer's mouth.