Hello Everypony!
This theory is concerning Princess Celestia and my reasoning behind why she never really does anything as well as why we haven't heard of Shining Armor until this episode.
We start out watching the mane 6 enjoying a picnic without a care in the world until a certain annoying purple dragon shows up to ruin the fun!
Spike presents Twilight with two scrolls that announce both the roles of the mane 6 in an upcoming wedding as well as the identity of the ponies getting married.
Princess Mi Amore Cadenza and Shining Armor.
The former being Twilights foalsitter from years ago and the latter being her brother.
"But InvisiBrony," you cry out in anger, "We have never heard of this brother before now!!!"
Well of course you haven't.
As Princess Celestia's student, Purple Princess in Training is most likely privy to a plethora of state secrets that other ponies are not aware of. Secrets that she would have to keep hidden from her friends.
These friends did not know Twilight as a foal so it's no big shock that they don't know her brother but why didn't she mention she had a brother before now?
In the "Slice of Life" episode we were introduced to the idea that there is an Agency at work in Equestria dedicated to the protection of the pony populace from monster activity by the confession of Bon (Sweetie Drops) Bon.
We also know that Shining Armor has a magical talent to create a shield that keeps certain monsters out of Canterlot. It is my assumption that Shining Armor is also a member of of this secret organization and a high up one at that.
This would explain why Twilight never talks about him. The fewer questions she has to answer about him the less chance she has of accidentally giving up state secrets.
Born with the talent of creating a "shining armor" forcefield he was scouted and inducted into the secret agent society where his powers were trained and perfected to be a defense against the changeling menace that threatened Equestria.
Since the forcefield is a projection of his own mental fortitude it stands to reason that the headaches he feels during the finale are from a Changeling having penetrated his mental barrier and picking away at it from the inside.
The reason he is being forced into the open and introduced is the doing of Queen Chrysalis who replaced his girlfriend and instigated the while marriage storyline.
In other theory blogs I have written I summed up my feelings on why Princess Celestia is pretty much a useless figurehead in terms of actually doing anything herself.
I believe that over time her magic has been drained by multiple uses of the Elements of Harmony especially when she was forced to do so alone and banish her sister forcing the elements to use a lot of her own magic to bolster their own to confine Nightmare Moon to her Lunar prison.
It makes sense that the banishment also removed a lot of Nightmare Moons magical powers or at least sealed them away otherwise she would have been able to free herself from banishment.
Her diminishing power combined with the increased power Queen Cheese legs has gotten from her Love Buffet explains how she was so easily defeated.
Celestia has spent years hiding the fact that her magic gets weaker by the day in the hopes that Twilight will be ready to take her place before the enemies of Equestria discover her weakness and take advantage of it.
As for Luna, she may have lost her powers in the banishment of 1000 years or perhaps she burned up her magical reserves becoming Nightmare Moon.
It may even be as simple as her not trusting herself to use her full magical abilities in fear of once again becoming her evil alter ego but that's a theory for another time.
So Sunbutt is down for the count and the mane six use the magic of violence to make their way to the magic of friendship but are captured and dragged back to the wedding chapel where Cadence and Shining armor are given the chance to interrupt the second rendition of "This day aria" with the power of their love.
Changelings feeds on love drained from unsuspecting ponies. Cadence manages to free Shining Armor from the clutches of Chrysalis but he is still too weak to enact his protection spell.
I would imagine that Chrysalis put a block on his magic, a drainage filter to syphon off his love that is still not fully removed.
Then Cadence fills up Shining Armor's love tanks to overflowing and much like pumping too much air into a balloon the force of their love combined caused the drainage trap to shatter and allow Shining Armor to apply protection once again as he and Cadence demonstrate their love in front of the whole city.
Cut off from her main source of food and power Queen Cheese legs is expelled from the city along with the rest of her insidious insect offspring leaving the pony population free to enjoy the open bar at the wedding reception.
Let's hope for the sake of Equestria the newlyweds stay together.
- InvisiBrony out