Happy Happy, Joy joy

Joy. What IS that stuff? Ineffable mood? Attitude? 
 
Describing what joy brings to any activity is like trying to answer, "Why Jell-o shots?" "Who would do Parkour?" or "What happened to the undercarriage of your grandfather's car?" 

That is, you can answer, but you can never really explain. And like many another, it's a quality easily identifiable at ten paces.

As an illustration, take a look at this strangely joyless rendition of the goofiest, happiest of dances:

It's easy to imagine these people are on their last legs, and that the Chicken Dance is the only part remaining of their memory of life above ground. 

This flying lawnmower (yes, I know this video has been around for ages. And yes, I understand how they did it. Don't be a buzzkill, bro) on the other hand, is utterly joyous: