Two. The light bulb you remove and the light bulb you replace it with.
Hella.
3. One to screw it in, the next to claim credit and the third to be a bot that reposts.
Three. One to change it while the other two argue about how old the old one is.
Three - one to change it, one to not-change it and one to both change-and not-change it.
Removed
Pollution.
