Teal said:Well Pluto was a planet when Sailor Moon was being drawn.
But it's not like pluto changed...our knowledge improved ;D
If we continued considering Pluto a planet, then we would also have to consider Ceres, Vesta and a big bunch of other similar bodies in the solar system...we just didn't discover them back then yet, to figure that counting those as planets really stretches the term out of what it was supposed to mean.
So the term planet was given a proper definition and by that Pluto simply isn't one of them. So in a way it never was a planet in the first place xD