How Many Pair Programmers Does It Take To Change A Lightbulb?

Short Answer
Two. Of course.

How long does it take?
More than 5 minutes, that's for sure.

Full Procedure

1. Try to develop a test for darkness
2. Rig up some sort of light sensing equipment and realise that this will only work when the room is naturally dark, so daytime is not the right time, unless the windows are boarded up
3. Board up the windows - they're not absolutely necessary anyway
4. Make an abstract interface for the lightswitch and insert it in place of the actual light switch, with the actual light switch connected back to it
5. Create an adapter for the existing bulb that adapts it to a testable bulb interface, and an adapter for that adapter to adapt back to the bulb socket
6. Reinstall the broken bulb with this new adapter
7. Ensure that the darkness test still holds
8. Use a torch to see whether the darkness test works with light at all
9. Go home for the night
10. In the morning, discover that someone else has noticed the bulb is broken and has replaced it in the space of a minute, wrecking your previous day's work
11. Spend the rest of the day drinking lattes with your mates and berating the short-sighted fool who change the lightbulb on his own and removed the boarding from the windows.

And there you have it
This stuff is true and not up for debate. Please let me know experiences of your own wih similarly trivial tasks which you have double-staffed and than dragged on long beyond the point where it was beneficial.