Mobile Fighter G Gundam/WMG

The Narrator is God
He seems to exist within the series and interact with it, but is also aware of the shows fictional nature and knows what's going to happen in advance.

The Devil Gundam didn't malfunction. Its AI is sentient & made a conscious choice to destroy humanity.
Seeing what mankind had done to the Earth, combined with Urube's attempt to use his powers for evil convinced him that humanity was rotten & it would be better to wipe them out & replace them with cute little Samurai-themed SD Gundams.

Allenby is the next King of Hearts.
Allenby has two very good incentives to ask Domon, the current King of Hearts, for training. Domon has already learned the secret to suppressing his anger in battle, which would allow Allenby to resist the Berserker system if it's ever forced on her again. Training would also give her an honest reason to be near Domon, since she's obviously still infatuated with him even if she refuses to act on it. Domon would likely agree to train her, as she's already demonstrated the ability to use the Shuffle's unique ki for both offense (the God Finger attack) and defense (her quick and complete recovery from DG Cell infection). As Domon's first and/or only pupil, Allenby would naturally be next in line for the title of King of Hearts.
 * Problem there. Shuffle Alliance members are destined to achieve the title, with the current holder recognising their successor via the mystical powers. There's also the fact that there tends to be a wide generational gap, since the SA are supposed to be an eternal secret group to defender humanity. Allenby is only 3-4 years younger than Domon, FAR too young to provide the needed gap. Plus she didn't really use any kind of 'Shuffle's unique ki'. She was just able to partner with Domon due to super robot logic.
 * I dunno, "unique ki" sounds like a type of super robot logic to me. The only people to share each other's moves were Shuffle Members (Gaia Crusher during the free-for-all, and I'm pretty sure one other occasion). Plus, there's still the fact that she recovered from DG cell infection in under a day, which took the intervention of a Shuffle member's power the last time it happened.
 * Could be she's the Alliance's Sixth Ranger, and got her powers offscreen from a character they never got to introduce. Red Joker, anyone?
 * Or maybe Big One?
 * Technically, Schwarz was the Sixth Ranger, occasionally referred to in supplemental materials as the "Wild Card"
 * Despite the fact that one of the Shuffle Alliance positions is "Black Joker", and the entire point of a Joker is that it is a wild card.
 * Maybe Allenby is that card with the rules for Poker on it.
 * While she cannot become the next King of Hearts, it is well possible Domon could train her in the techniques of the Undefeated of the East. The fact that she managed to copy his God Finger instantly would indicate she's up to the task.

Everything was part of a plot to destroy The Statue of Liberty Cannon
DG cells, Master Asia, Devil Gundam, Kyoji Kasshu, Ulube Ishikawa, Wong Yunfat, and even the Death Army were pawns in an elaborate (and successful) scheme by Neo Japan to destroy Neo America’s most powerful weapon - The Statue of Liberty Cannon.
 * What role did Douglas Macarthur, who was operating the Statue of Liberty Cannon, have in this consperacy?

Master Gundam can be piloted backwards
In one episode Master Asia crossed his arms and Master Gundam's arms were doing the mirror opposite.
 * Allows Master Asia to pull an absolutely epic I Am Not Left-Handed!

Simon from Gurren Lagann is Domon's son!
Or, at the very least, his clone:

Don't believe me? Check this out:

http://www.youtube.com/watch?v=Gca UL Pp N Fyg
 * He certainly wouldn't be the first.

Domon is descended from Noriko Takaya.
Just listen to those insanely Hot-Blooded Attack Calls!!

the devil gundam is a reaper or based on reaper tech

 * think about it, it desires the extinction of humanity, has the ability to revive dead organics as zombies (AKA husks!!) and appears to be able to warp the views of others towards it's own (AKA indoctrination!!)