So, I have this theory about the Season Six Finale (Somewhat related to The Fault in Our Cutie Marks) · 2:00pm Sep 12th, 2016
Just in case you don't want to know for spoilers...
Okay, we good? Alrighty. So, in season four, we had a story arc in which guest characters gave each of the Mane Six a key that would eventually unlock the Rainbow Power box, which allowed them to defeat Tirek. Throughout the season we had one of these guests appear, have a lesson for both them and the Mane Six member to learn, and give the fandom story fuel to play with.
Kidding, of course, with that last part.
Now so far in this season, we've gotten three guest characters in their own episode leaving a similar impact: Dragon Lord Ember, Thorax the changeling, and now Gabby the griffon. All three are of races other than ponies, and all left/ignored their kind's general way of life and accepted ponykind's (Marekind? Horsekind?) instead. I'm thinking that this is part of an arc they're doing to not only expand on the lore of other races, but to introduce a plot-point of the finale.
So maybe they combine forces to defeat the annual threat of the finale? Unite their own races to do the previously-mentioned thing? And are there more examples going to be brought in for future episodes? I hope so!
And no, I'm not going to the MLP wikia to see summaries of future episodes to find out. I prefer this theory to unravel as it was intended to be.
[EDIT] Okay, so I was . . . one third right (?)
