Wild Arms/WMG

Word of God is wrong, and the games (and anime!) take place on seven different planets.
All right, this is mostly Fan Wank, but isn't that one thing WMG pages are for? Filgaia (or, rather, Falgaiya or whatever the anime's Blind Idiot Subtitling eventually decided to call it) in Wild Arms: Twilight Venom is explicitly stated to be an Earth colony gone rogue. Advanced 3rd's Filgaia is supposed to have been colonized by people fleeing Terra. "Filgaia" itself isn't a perfect translation - "Fargaia" is also used, apparently interchangeably. Now, what would be a good name for a dispersal of humanity across the sea of stars? The Far Gaia Initiative, or something like that.
 * ...Translated information from the Japanese fact books mention that they're different Filgaias in different universes. Did the creators change their minds after Wild Arms 3 or something? What's the source of that Word of God?
 * It was at the bottom of the main page, though it might not be there much longer....
 * Having contacted someone who talked to the person that was the source of the above translated information, it's become apparent that, uh... they're both from official material. Just that the single Filgaia version is the latest official stance. Huh. The more you know.

Alternately, the numbered games take place in exactly two timelines.
The key is the "Four Witches" In-Game Novel. Kain in it came from the time of Hauser Blackwell, a world in which the empire he encounters in the past was only defeated by a rebellion containing a version of the Wild Arms 1 main characters, after an Enemy Mine situation against the Metal Demons. Emma Hetfield's researches in this time line led to the age of golems, and thus eventually to the Veruni emigration; also, Wild Arms 5's TF system is related to the Marduk project of Wild Arms 4. Kain's travels led to the timeline of the first three games, which happened approximately in order. The version of history given at The World's Footprint in Wild Arms 3 is just mildly misinterpreted, mixing together events that happened centuries apart.

Ragu o Ragla is immortal and will eventually destroy the world
According to Word of God, all of the Wild Arms games take place on the same Filgaia yet each game has Ragu o Ragla to fight. Meaning that the Eldritch Abomination is either immortal and keeps reviving or there's more than one and they keep coming to Filgaia and somehow get sealed. Either way, it's going to eventually wake up, go on a rampage on Filgaia and destroy the world.
 * So? Destroying Filgaia and rendering it a near-uninhabitable wasteland for a period of centuries to millennia happens so often you probably need to take a number and wait your turn to do it.