One. No, two. No... How many do we have on the truck?
or
10. One to hold the bulb and nine to rotate the ladder.
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
There are footprints in the butter.
or
None. The darkness will cause the bulb to change by itself.
or