Phantom Responsibility · 11:56pm Feb 2nd, 2016
"Phantom Responsibility. Tell me, have you ever heard of anything like that?"
"I... n-no, I can't say that I have."
Sunset Shimmer sighed and nodded. "I'd figured as such. But it's the closest description that we've got, to what's happening here... or rather, over there."
They both looked over, where Twilight Sparkle was being held... by Twilight Sparkle. More specifically, it was the human, local Twilight, who was being held by her other self from Equestria. It was obvious from anyone who saw, even though they were the same person, their temperaments were quite different. Twilight H stood at nervous rest, taking in Twilight P's calming, comforting presence.
"Say that while a version of you has been nothing but a model pony- er, person, their entire life... you find out much later, that another version of you, once slipped down a dark path. If you were the person who hadn't... would you feel responsible, for the person who did?"
Her companion worked that one over in her mind, expression contorting. "... even if it wasn't me... it's still, well, me... I... that's a tough one."
"It is, isn't it?" She leaned back and sighed. "The Human Twilight, the one who's native here, had such a lapse not too long ago. And the other Twilight... well... Simply put, she feels responsible. Like her simply existing as a person allowed it to happen."
"But it wasn't her."
"And yet at the same time it was. Hence the 'Phantom', in Phantom Responsibility." Sunset looked over to the two bookish girls, her face unreadable. "Thankfully, Twilight being who she is... she wants to try and help her other self, in any way she can. Part of that is her being a friend, but I think part of it is also her feeling responsible. It's her way of helping make things right."
The girl sitting across from her nodded, quiet for a second, before she looked back. "... why are you telling me this?"
Sunset Shimmer sighed once more, before lifting a hand, and placing it on Sunset Shimmer's shoulder. "Let's just say, while you were in Equestria... I wasn't exactly an angel myself. And the last thing I want you to do, is to start losing sleep, over me."
Whoa. This may be one of the most fascinating hypotheses for what happened to human Sunset that I've seen yet.
Awe... some.
I like this premse. I like it quite a lot.
Can this be a thing? It would be awesome if this turned into an actual thing, two worlds collide story.
3729387 Sunset Shimmer is a badass changeling hunter with a sledgehammer that she named Mark Antony.
3729387
It's yet another story idea I've been congealing, one in which the Sunsets more or less traded worlds. While Sunset P was taking over CHS, Sunset H was caught up in the workings of a small pony town, west of the Crystal Empire...
3729546 PLEASE make this happen.
I would read it in a heartbeat, as I'm sure many others would. 
3729875 Ditto, this sounds like a brilliant twist
This is beautiful as always. Your works consistently blow me away and I'm adding my voice to the throng begging for this to become a fully fleshed out story.
This is amazing and I want more so badly.