So I've begun working on an idea that, for some reason, popped into my head recently. The basic idea is that Sunset, when she abandons Princess Celestia, doesn't end up in Canterlot High. But on Earth.

At the height of the Calamity War. With so much not shown of the war during the series, it leaves plenty of room to work with I feel. Of course Sunset would not be the only Equestria Girls character there.

I had thought of having the rest of the Rainbooms be there as well. Not transported there by accident, but born and raised in this universe. All of them would be drawn into the battle just to survive the Mobile Armors.

And since it wouldn't be a Gundam crossover without them, I have an image of Sunset piloting the Barbatos, and the rest of the girls also getting to pilot their own Gundam. With 72 Gundam Frames at the time of the war, I think there's plenty to work with.

Thoughts? Ideas? I'm open to anything at the moment. This is still in very early stages.

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We don't know much of the Calamity War as there is little information to go by.

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Which makes the idea I have work even better, since now I can make some things up for the story, and not worry too much about going too much against canon.

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I'll admit that this previous idea was good as you had at least a rough idea: https://www.fimfiction.net/group/201076/gundam-team-harmony/thread/296248/my-little-pony-equestria-girls-x-mobile-suit-gundam-iron-blooded-orphans-crossover

Plus, I gave ideas for more Gundam names. Here is two ways for the Gundams to come into the picture: The first idea is that Sunset finds her Gundam on Mars and when the Hashmal Mobile Armor wakes up, Rustal upon hearing what went on thanks to McGillis and Julieta telling him and grilling Iok more greatly than in cannon (not making Rustal a saint here let's be clear) of how it woke up (this is before the Coup though) decides to punish him by not only removing him from active duty, but also make him hand over the Kujan's Family Gundam which is the ASW - G - 63 Gundam Andras while the others are awakened from their crypts (Rustal's family has a vault and possibly a Gundam in it).

What the girls don't realize is that Rustal is looking for an excuse to get rid of McGills and Tekkadan in one shot while making himself look good in the public eye. Only Applejack suspects Rustal's true, dishonest intent.

The second is all of them are found not far from where the Hashmal was found (similar to how the ASW-G-64 Flauros Gundam was found) in what would be described as six of the Seven Gundams that the girls use sacrificing themselves to stop the Mobile Armors on Mars while the other one ends up being found in a salvage operation gone wrong (the pilot of the ASW-G-72 Andromalius being KIA while denying the fallen Gundams and Mobile Armors to a group of long-dead pirates).