Most people have encountered painful car-door sparks, as well as those wintertime sparks from doorknobs and large metal objects.
Unexpected doorknob sparking only seems mysterious because of a misconception.
As children, most of us learn the trick of scuffing our shoes across the carpet in order to charge our bodies. The need for friction is a widespread misconception. It's true that the friction can increase the charge-separation process. However, opposite charges are separated whenever two different insulators touch together. This is enough to separate the negatives from the positives and create imbalanced electric charges on the bottoms of your shoes.