Because they had so many knights.
or
Only one. But he'll leave a big puddle of spit on the floor underneath him.
or
Because E.T. eventually went home!
or
Three: One to screw it in, and two to talk about how much better it is than with a man.
or
1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or