Norse code.
or
None. The darkness will cause the bulb to change by itself.
or
The League of Extraordinary Con Men.
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Nothing, it shuts them up!
or
Only one, but she/he'll have to go out and buy the light bulb adaptor card first, which is extra.
or
Three. One to climb the ladder while the second kicks the ladder out from under her. And the third to say, "I knew that was too high for you dear."
or
[A Condesending con descending]
or