Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
or
Do you swear to pull the tooth, the whole tooth and nothing but the tooth?
or
Three: One to screw it in, and the other two to help him down off the keg.
or
Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes (knowing that it's already burned out).
or