Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
or
A centipede with a wooden leg.
or
Should've been called Look Who's Hawking, that's my only criticism.
or
Tooth-hurty.
or
I guess that finally answers the question about how much Donald Trump is actually worth.
or