Yup, it's all about the shoes. Basically if you're wearing a certain type of sole it will build up a static charge which will release when you touch something metal and give you a shock. This could be the car or anything metal like the aforementioned spoon or even a metal banister.
I have one pair of shoes that does just that - it's a pain - litterally! Luckily I don't wear them often.
An ex-girlfriend used to get so p1$$ed off when she got a shock off the car when she wore certain boots she very nearly kicked the door in frustration. Good job I was driving a Micra at the time! (I was poor and it was a long time ago!)
I wouldn't let her near the Supe if I was still with her now!!
Geeky explanation over - back to work!