His son, because he's a little Bigger!
or
Because there's no one else to wag it for him.
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
Billllyuns and billllyuns. Light bulbs are part of the interstellar "goo" that pervades our universe; they are star stuff.
or
Because he wanted to tie the score!
or