None. Agnostics question whether electricity really exists.
or
10. One to hold the bulb and nine to rotate the ladder.
or
Seven. One to change it and the other six to sing about how good the old one was.
or
Between you and me, something smells.
or
Because it goes good with chips.
or
Only one. But he'll leave a big puddle of spit on the floor underneath him.
or
Two. One to hold the bulb and the other to rotate the planet.
or