By relocating it to a casino!
or
Because E.T. eventually went home!
or
One has claws at the end of its paws and one has a pause at the end of its clause
or
None. There never was any light bulb.
Notes: Probably the only really good light bulb joke of 1984.
or
Two. One to assure the everything possible is being done while the other screws the bulb into the water faucet.
or
Seven months old.
or
The barman says "Sorry we don't serve food in here"
or