One. But he doesn't screw it in, he just holds it and the world revolves around him.
To screw in the lightbulb.
A: A fish!
Three. One to change it while the other two argue about how old the old one is.
100. 1 to change the light bulb and the other 99 to complain about how the old light bulb was much better.
Just one she hokds the blub and the world revolves around her.
He holds the lightbulb and the world revolves around him.
One narcissist. The narcissist holds the lightbulb in the socket and waits for the world to revolve around him.