Planet?

Pluto. The ninth planet. Or it was until a few years ago when scientists confirmed that it was, in fact, not a planet. Pluto isn't a planet because, in order to be a planet, you have to:

1.) Orbit around a star.
(Pluto does this, so it might be a planet...)

2.) Have enough gravity to pull itself into a spherical shape.
(...Pluto does this too, so maybe...)

3.) "Clear the neighborhood" of its orbit.
(...Oh no! This is the only thing Pluto has unchecked! It's, sadly, not a planet.)

The Crab Nebula is not a planet because it doesn't orbit around a star, it's not a sphere, and it doesn't really have an orbit. But that's okay, because its massive size makes it awesomer than a planet!


[Sidenote to Pluto--
It's okay, Pluto. I'm not a planet either ;) ]