The more I research the subject of Planet X, the more I lean toward this theory. Every Ancient Wonder - from the Pyramids at Giza, Egypt, to Gobekli Tepe in Turkey, to the Heads on Easter Island - seems to suggest that a superior race of beings once came to planet Earth. And there is also compelling evidence - such as the word "Hu-Man" - which supports the notion that these superior beings created mankind.
Hu, according to the Oxford English dictionary is a Sanskrit word from which the word "God" can be derived. Add to that, the suffix 'man', and, well... you do the math.
The show Ancient Aliens on the History Channel gives excellent coverage and insights in to the this topic. And though Planet x is not the focus of this program, they often provide information which directly supports the planet X idea. Here is one episode of Ancient Aliens - a show I like quite a bit, and watch whenever I can.