Sorry, light bulbs are an evolutionary dead end.
or
A funky chicken.
or
A vicious circle.
or
Big holes all over Australia!
or
Just one, but he/she will spend hours checking for technical problems.
or
Twenty. One to hold the bulb, two to turn the ladder, and seventeen on the guest list.
or
He gave her a ring.
or
Because it goes good with chips.
or
To get to the udder side.
or
Because all his other wives support Hillary.
or