I suppose there are many punchlines, but the one I like the most is ...
None ... they like to stay in the dark.
Then there's ...
Twelve. They all live in Brooklyn, and they have to keep changing it every day for "new light."
Also ...
Three. One to screw in the bulb, and two to knock on your door and twll you about the new light.
And ...
None. They're always getting "new light" from Brooklyn.
Another favorite ...
I don't know - I didn't let them in to find out.
Last, but not least ...
It takes as many as The Watchtower says it takes!