Anyone in England who'd promised something "when pigs fly" might have had to make good on their vow on Dec. 2, 1976, thanks to a stunt by Pink Floyd gone slightly wrong.
On that day, the band was planning an album cover shoot for their 10th album, the appropriately-titled Animals. It was bassist Roger Waters who came up with the concept: an image of a pig floating over a soon-to-be-disused power station in Battersea, on the banks of the river Thames. (Animals opened and closed with a two-part track, "Pigs on the Wing," and "Pigs (Three Different Ones)" opened the album's second side.) Australian artist Jeffrey Thames and German zeppelin manufacturer Ballon Fabrik collaborated to create a 40-foot balloon - which the crew nicknamed "Algie" - to float in place over the power plant as photos were taken.
Of course, the best-laid plans of mice and men (or pigs, or Pink Floyd members) often go astray, and the Animals gang had two big issues. The photo shoot was slowed by bad weather, and a marksman commissioned to shoot down the balloon in case it broke free from its moorings was only hired for a day's work. Those two factors combined, and Algie was soon on the run - er, float.
The passage of time and the building of myth has led to a lot of tall tales about that day. Some contend that flights at Heathrow Airport were grounded after a pilot caught the balloon in his sights and caused panic. Another story goes that when the balloon finally landed in Kent, a local farmer was very displeased, as all his livestock was spooked by the descent of a much larger animal. Ultimately, the photo shoot went without a hitch for a third day, but the final cover ended up being a composite of shots from across the days.
Now, of course, good old Algie is a rock icon - a symbol against conformity and tyranny while also being a symbol of when great rock ideas go a little astray.