One is a blood-sucking parasite, the other is an insect.
or
None. Bill Gates will just redefine Darkness® as the industry standard.
or
Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
or
10. One to hold the bulb and nine to rotate the ladder.
or