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When someone stands up from an office chair, they also create the ideal conditions for static electricity. If the air is fairly dry, and they have sat and squirmed in that chair for a while, then they will have built up a little bit of charge. However, their body and the seat of the chair act as a capacitor, as they are effectively two objects (plates, in a capacitor) separated by an insulator. So, as they stand up and the distance between the two "plates" increases, the capacitance decreases, but since the charge held remains constant, the voltage must correspondingly increase.

It can be a neat trick to stand up from an office chair and then point your finger at your co-worker's ear.

It's also one reason why I am extra-super-careful to ground myself when digging around the guts of any computer systems when I'm sitting on an office chair.