Wendy's mom has a lamp in her house that lacks a standard on/off switch.  Instead, it magically turns on when you touch any part of its metal base.  This baffled me for many years, even when I recently proved that a sock doesn't work, though a metal object does.  It turns out it's kind of like the lamp's metal structure is a circuit with very low current going through it at all times.  When something (i.e. a human or a metal object) does something to interrupt this circuit, it responds appropriately.  I didn't get a chance to test this, but apparently these lamps are tuned in such a way that a cat's touch won't set it off; it only recognizes the electrical capacitance of a human, which is based on mass and volume and alcohol content (kidding).  Next time I visit:  Does Prairie the Cat make the lamp turn on? #science