Two. One to assume the ladder and one to change the bulb.
A': None. If the government would just leave it alone, it would screw itself in.
or
Five: One to change the bulb and four to pull the ladder out from under him/her.
or
Bozo The Clown has real hair on his head.
or
Because 7 ate 9.
or
It ran out of juice!
or