* Pluto is no longer considered a planet. In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet. This is because it didn't meet all the criteria for a full-fledged planet.

* There is no official ninth planet. While there is evidence suggesting a large object might exist beyond Neptune, it hasn't been directly observed yet. It's currently just a hypothetical object.

So, nothing "crosses paths" with Pluto to become the ninth planet, because Pluto isn't a planet anymore, and the hypothetical ninth planet hasn't been found.