Board Thread:General Discussions/@comment-1030114-20140726200851/@comment-25285745-20140923010128

Ghidorah being the product of some unknown alien race's genetic experiments could offer a better explanation for why he looks the way he does and how he gets to Earth, but the introduction of sentient alien races would expand Gareth's universe into unneeded territory. That's why in my opinion an ambiguous origin works better. For all we know, he could be the product of another alien race, but we can't be sure. It is all left up for the viewers' speculation. As for him arriving at a convenient time, perhaps there could be a reason for it. Perhaps satellites in the Earth's atmosphere have drawn Ghidorah's attention. Perhaps Ghidorah is drawn to Earth by radiation. Millions of years ago he came to Earth to feed on its radiation and caused the Permian extinction and then left when the radiation was depleted. Now, the large amounts of radiation produced by mankind have drawn Ghidorah back to Earth. This could also explain Ghidorah's rivalry with Godzilla. Both require radiation to survive, but Ghidorah takes more than he needs, devastating the planet in the process.

Again, it's all up to Gareth, but I'm just offering explanations for some possible routes he may choose to take.