Make sure one is a match!
or
One's a spineless, poisonous blob. The other is a form of sea life.
or
As many as possible, and don't *ask* what they do with the old bulb.
or
None: A `Real Woman' would have plenty of real men around to do it.
or
they always take things literally.
or
Five: one to handle the bulb and four to contemplate how David Sanborn would've done it.
or
Just one, but he/she will spend hours checking for technical problems.
or