And now we know… spoilers…
 
That IS the Element of Magic! I don’t know why it looks different, but at least that explains why it’s so important to get it back.

@MLP-Silver-Quill  
I am torn as to what jet princess tiara is. I am disinclined to believe that it’s an ascended form of the element of magic, unless it is supposed to be all six elements merged. It may be a different object entirely.
 
Also, I am suspecting that EQG is actually a midquel for MMC, as opposed to taking place afterwards. Twilight has not been crowned yet, and that is why she must retrieve the crown. EQG may also be where that animation from Hot Topic of her awkwardly trying to fly came from, since it takes place before her coronation.

@Beatfox  
Until we get more solid info, I’m considering that a fan theory. The gem is similar, but that can be easily duplicated.

*died, not dotted, lol

@SeraphimDawn  
That’s because Twilight dotted, and everything afterwards is just Celestia making up a happy fantasy. (Or so I have read on 4chan.) That’s why the episode makes so little sense after she (incorrectly) finishes the spell that killed her.

@SeraphimDawn  
They didn’t even look worried.

@bboifatz  
And they just casually walked out of the library, not even thinking of what happened to Twilight, in what could’ve thought of as ponyslaughter(manslaughter).

@Beatfox  
I wonder if that theory that Twilight’s new crown is an algamation of all 6 elements is going to come up again? We never saw what happened to the other 5 after Twilight got incinerated.

@MLP-Silver-Quill  
@JJMDude
 
It’s a new form for the Element of Magic, just like (pony) Twilight acquired a new form. Even though it’s not made clear what happened to it during the magic zap, the big cutie-mark-shaped jewel ought to be a pretty good indicator of its identity.
 
Think of it like Gandalf the Grey’s staff vs. Gandalf the White’s staff, or the sword Narsil vs. the sword Andúril. Yay, more LotR comparisons!

So she gets her dumb crown back. Looks like I saved $10 today!

@JJMDude  
Or… oh jeez, she lost the Element of Magic!
 
Quick, someone call the trans-dimensional lost and found!

@MLP-Silver-Quill
 
That’s… huh. I’d never noticed that before.
 
Wait, that’s odd. She was wearing it when she got zapped into the astral void with Celestia, and it wasn’t left where she’d been standing after she vanished. The hell?
 
So, does that make it a continuity flub, or did she fuse with the Element itself, or…
 
Well, I guess that’ll be made clear later. This crown must mean something if she’s gone in after it though, goes without saying.

@JJMDude  
That’s the crown from her coronation, not the Element of Magic. The base doesn’t curve downward and doesn’t have any of the blue gems.

@MLP-Silver-Quill  
…It’s the Element of Magic…
 
I think they kinda need that, being an integral part of Equestria’s defenses and all.

@Background Pony  
I can’t figure out why it’s so important that she has to go dimension-hopping to get it back.

look at those tiny arms goddamn
 
you a t-rex, girl?

What I want to figure out is who stole it and how it ended up in the prom.

@Blissey1  
The Nazis briefly discovers that the troops who got turned into unicorn can use magic. Combine this with their superior Tech and the fact they caught the Equestrians off guard, the Equestrian ponies fell back.
 
However, thanks to the Equestrian’s being more experienced with magic and their courage and willingness to protect their land, fought back. They’ve also learned to use some of the machines they’ve managed to capture from the invading forces back at them.

So it was her crown that was stolen. Canon-Twi, you better keep a better hold on it than this floozy version of you.

@SeraphimDawn  
classic magic vs. tech battle ensues, I suppose.

After watching the Full Metal Alchemist movie.
 
What happens if Nazis from the Human World tries to conquer Equestria by sending troops and machines through the magic mirror in order to gain access to the magic of the land? The Ponies of Equestria find themselves having to fight off the invading Nazi forces(who became ponified upon crossing the mirror) for the fate of Equestria.

Well at least we know the stolen crown is actually Twilight’s crown, thus it holds some sort of significance.

Oh, she found it! Well, that was fast.  
I guess there isn’t gonna be a movie after all.

And that’s how Twilight Sparkle conquered Earth in the name of the royal sisters.