None. They will never find one that burned as brightly as the first one.
or
Two. One to assure the everything possible is being done while the other screws the bulb into the water faucet.
or
Three: One to screw it in, and the other two to help him down off the keg.
or
Two — one to change the bulb, and one to write a song about how good the old light bulb was.
or