Five. One to screw it in and four to tell him how bitchin' he looked doing it.
or
It takes them a long time to swallow their pride.
or
He presses the paws button.
or
None, because people who glow in the dark don't need light bulbs.
Note: Topical to the Chernobyl Reactor disaster of 1984.
or
To hide in a bag of M&M's.
or
He wanted his soil to be rich!
or