One is a blood-sucking parasite, the other is an insect.
or
None, because people who glow in the dark don't need light bulbs.
Note: Topical to the Chernobyl Reactor disaster of 1984.
or
Two — one to change the bulb, and one to write a song about how good the old light bulb was.
or
Thoreau editing Thorough.
or