There are thousands of asteroids whose orbit in the Solar System crosses that of Earth. And we have a little acronym for them - NEOs: near Earth objects. And our biggest goal is to try to catalogue them, so we know in advance if one is going to put us at risk.
Pluto's orbit is so elongated that it crosses the orbit of another planet. Now that's... you've got no business doing that if you want to call yourself a planet. Come on, now! There's something especially transgressive about that.
When NASA says they're going into space, they don't mean up and back. They mean orbit.