Actor Allusion: When Aeon reveals his backstory and mentions St. Germain, Rarity thinks the name sounds familiar.
Creator Backlash: The author has admitted that the first arc in Adventure was a very boring excuse at World Building and laying groundwork for the rest of the stories proper in the series, and that if he could, he'd go back and rewrite it (but won't because it'd be a waste of time and effort).
Creator Breakdown: Currently (as of September 2014), the author is going through a real life Trauma Conga Line and suffering depression as a result, which is naturally slowing down his writing. He's stated his intention to keep writing, however.
What Could Have Been: Originally, Marble/White Dwarf was just going to be Actrise in disguise. But so many readers saw that coming, the author decided to rework the character.
In addition, Word of God is that Shatterstorm was actually supposed to die early on in the story.
Pinkie Pie was supposed to be the one that Shatterstorm and Spike ran into in chapter 2 of Equestrylvania Adventure, but for the sake of fleshing out the plot, it was made Rarity instead.
Soarin's first appearance got pushed back for pacing reasons.