It’s called Williams Syndrome. I heard this come up on an episode of House and it piqued my interest enough to dig a little deeper. WS is a genetic disorder that’s inherited at birth. It’s caused by a lack of having a few specific genes. The disorder leads to an elfin appearance and a below average IQ, but it also comes with one particularly awesome side effect – people who have WS are perpetually happy and are the friendliest people on the planet. Take a moment to watch this short clip on this rare (1/20,000) disease.