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
Bike helmets don't fit hippos
or
Your wife comes back to you, your dog returns to life and you get out of prison.
or
The baker, because he has lots of dough.
or