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
I don't know. I didn't think sheep could knit
or
They cell it.
or
When it's ajar!
or
Five. One to change the bulb and eleven to say they could do it faster.
or
In their Sleevies!
or
Because they don't fit on a ironing board
or