ONETIME- Sparks flying: What happened when the switch flipped
One time, I asked a middling electrician friend of mine along to help me hang a light fixture that was lovingly made by the homeowner's father, who was a retired dentist. He built her a beautiful stained-glass fixture that weighed about a hundred pounds; it was all solder-jointed. So it took the installation of a fan bracket that went across the ceiling joists, and then it needed to be rewired.
So we were working on it, and the homeowner's husband came home, and he knew me, but he didn't know my helper. And he introduced himself to the helper, and asked us, "How much do I owe you guys?" And I said, "You don't owe us anything," and jokingly added, "I especially wouldn't pay my helper until you see the sparks fly."
So he left, changed his clothes, and came in, and it was time to check the light, so I said, "Hit the switch." He hit the switch– and then the fireworks started. The fixture went Blam! Blam! Blam! Blam! Blam! Blam! Blam! Blam! Blam!
Flames shot out the tops of the fixture, embers fell to the floor, and I screamed at him to turn it off.
He said, "Pete, what the hell is going on here?"
I said, "I don't have an answer."
He goes: "You told me ‘Wait until the sparks fly'—Is this some kind of a joke? I don't appreciate it."
What had happened was, he had tightened the set screw down on the receptacle on the plug where you put the light bulb in where it contacted the neutral and the hot.
So the lesson here is: follow the manufacturer's instructions on proper grounding and proper wiring. And when someone tells you they're an electrician, make them show you their card!