What were your theories for Sunset Shimmer before EQG was released?

[Wardaddy 470]

In the run up to EQG, none of us had any idea about this Sunset Shimmer character, until the EQG trailer showed up. Almost instantly, theories began popping up left and right. Heck, I even made my own one, and it is as follows:

 

Before the events of EQG took place, Sunset was Celestia's student, protégé and master of magic. One day, Celestia taught Sunset the basics of performing a teleportation spell (like we saw in the beginning to the movie, when Sunset out-teleported Twilight and made off with her crown to the human world). On her first attempt to perform the spell, where she'd teleport to Ponyville and back, something went wrong and Sunset was instead teleported to a far-away province in Equestria. Celestia tried to re-open the portal to get Sunset back, but couldn't, and so she was left no choice but to deem Sunset a lost cause, beginning her search for a new protégé (which is where Twilight comes in).

 

Meanwhile, Sunset fails to re-open the portal as well, resolving to perfect the spell until she could get back to Canterlot. Having spent months doing exactly that, Sunset finally manages to teleport back to Canterlot, only when she gets there, she is greeted with a sight that tears her hopes and dreams (and her heart) to shreds. (The following is a revised version of my original theory, so bear with me)

 

Sunset teleports back into Canterlot at the exact time Twilight was coronated Princess of Magic. Seeing Twilight standing where she should be standing, anger begins to broil deep down within Sunset, coupled with a demand for answers.......and vengeance. After the coronation, Sunset tracks down Celestia in Canterlot Castle, demanding to know why she was replaced. Celestia (surprised to see Sunset again) tells her that she deemed Sunset to have been trapped behind the portal with no way to get back, and so replaced her with Twilight. Outraged, angry and vengeful, Sunset threatens Celestia that unless she gives the crown to her and lets her be the princess of magic as was intended, she would take it by force. Obviously, Celestia refuses, and Sunset then swore that she would return to get the crown, and when she got it, she would rule Equestria with an iron hoof. Just as Celestia calls for her guards to arrest her, Sunset runs into the depths of the castle, holing up in the room with the portal to the human world. As the guards close in on her, Sunset slowly backs up against the mirror, before accidentally falling through it. In the run up to Equestria Girls, she then resolved to use the human world as her safe haven until the heat from the guards passed off, taking the time to devise a plan to take back the crown. Every now and then, she would re-enter the pony world to eavesdrop on news relating to Twilight, which wouldn't come until Celestia arranged the meeting with Luna, Cadance and Twilight at the Crystal Empire, where Sunset then planned to infiltrate the castle and take back the crown. Cue Equestria Girls!

 

Well, that's my theory. If any of you bronies have a theory, then lets hear it!   
 

[RubyVesper 100]

Discord seemed to be able to have discordant influences in stone, as seen with the CMC. I think he might've used Sunset Shimmer as a plan. His influences could've easily caused Sunset Shimmer to renegade, and steal the crown to leave Equestria in a chaotic state where he can easily get his "throne" back.

[Scootalove 10,692]

My theory was Trixie being an ally to Sunset Shimmer to steal Twilight's crown and plunge Equestria into anarchy and other destruction in the other parallel universe.

[Buttonmash1973 1,026]

Sunset Shimmer must have met with Twilight Sparkle before since she took the crown from her. By the way I was surprised there was no carnival as there was carnival themed figures.