In chapter 6, when confronted with a talking purple unicorn, Mike…manages not to freak out, mentioning that he "learned a long time ago how weird the world can get". This starts making a lot more sense when we learn that this is happening on the same Earth as G.I. Joe and G1 Transformers.
Nightmare Moon is trying to bring about The Night That Never Ends, just like Tirac. Because she's heard stories about him.
Alternately, this leads credence to the theory that Tirac was the one who corrupted Luna. Which was later confirmed.
Chip can walk now, because he's wearing an exosuit like Jessica Morgan in "The Return of Optimus Prime, Part 1 & 2".
Granny Bonnie, the creator of the world where Ponyland/Equestria is, is named after Bonnie D. Zacherle, the creator of the original toyline that started it all. Faust the Scribe is named after Lauren Faust, who revitalized the franchise with My Little Pony: Friendship is Magic.
In United We Stand, President Abernathy almost seems to bend over backwards to avoid having to fight Empress Celestia and her forces. Given that he's a former GI Joe, and lived through things like the Decepticons, the Inhumanoids, and more, it makes sense that he's not immediately trying to jump in and fight yet another war, yet it also explains how unfazed he is about the whole thing- it is literally not the first time that someone has come to Earth to pick a fight.
"The Conversion Bureau: United We Stand", chapter 7 confirms that the Inhumanoids are amongst the alien threats faced by humanity in the 20 years since the Rainbow Bridge first opened.
If the Wendigos were driven off, why are the Founders still frozen in ice and conscious?
That might be revealed in a later story.
Tirac might not stop at ruling Equestria, he may have his sights on Earth next.
Megan's kids had nightmares about Tirac after reading her first My Little Horsey book. What if every other kid did?
It's quite possible many did. Several villains from real life popular children's media - such as Maleficent - have been known to cause nightmares.
In The Conversion Bureau: United We Stand, it's revealed that ultimately, the Decepticons split into two factions. Starscream took a bunch of Decepticons and settled a small planet of their own. He comes to Cybertron to barter the Decepticons' aid to Earth in exchange for a serious peace treaty. He gets to be ruler of the Decepticons, his faction isn't wiped out by the alliance, it stabilizes a region of space, and most importantly, it draws Decepticons away from Galvatron's faction. Meanwhile, the other faction of Decepticons follows Galvatron, who has gone nuts, his faction has low morale and supplies, and is more of a nuisance at this point than a full threat.
This universe also suffered from the Hate Plague. Were the Williams/Richards safe somewhere when it happened, or have they also got infected?
Though it should be noted that even if they were, Optimus cured them shortly thereafter, so it probably wasn't too bad.
, the creator of the original toyline that started it all. Faust the Scribe is named after Lauren Faust, who revitalized the franchise with My Little Pony: Friendship is Magic.