Five. One to screw it in and four to tell him how bitchin' he looked doing it.
or
Ah-choo-choo!
or
Five: one to handle the bulb and four to contemplate how David Sanborn would've done it.
or
Twenty. One to hold the bulb, two to turn the ladder, and seventeen on the guest list.
or
Does it have to be a light bulb? I've got this neat candle holder...
or