Only one, but the light bulb should be willing to change.
One, but you can be sure a whole Reddit community will appear to expand the joke, make it funnier and eventually run it into the ground.
None. PETA can't change anything.
Many hands make light work.
A: Three - one to change it, one to not-change it and one to both change-and not-change it.
A magician makes rabbits appear in hats, while a psychologist makes habits appear in rats.
Because he feels for everyone.