Peanut butter and jellyfish.
or
None, because they were copycats
or
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
When a rooster wakes up in the morning, its primal urge is to cluck defiance.
or