As many as possible, and don't *ask* what they do with the old bulb.
or
I said, "Are you two an item?"
or
I don't know. I didn't think sheep could knit
or
None, but it takes at least one to sit and pray for the old one to go back on.
or
Three - one to cast the bulb into the outer darkness, and two to catch it when it falls.
or