Two-lips!
or
Five. One to screw it in and four to tell him how bitchin' he looked doing it.
or
Two — one to change the bulb, and one to write a song about how good the old light bulb was.
or
1,622. One to tell the original joke, and the rest to submit give some minor variation of it! For example:
or
He was tired of working for peanuts.
or