Five: One to change the bulb and four to pull the ladder out from under him/her.
or
The owner got tired of the (w)hole business!
or
It's not a shrub, it's a lemon tree my dear Watson.
or
1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or
Can I have your hand, hand, hand, hand, hand, hand, hand, hand in marriage?
or