All we know is that Twi suddenly finds herself standing in an unfamiliar room (which looks to be the throne room of the old castle before it was ruined), and Luna talks to her as if she’s Celestia before transforming into NMM.
@Theater Critic
Me, the artist of >>379815, and several people in the comments of said pic, for starters.
The Nightmare Moon return/flashback/whatever, to be honest, has me slightly worried rather than vibrating with anticipation. (The rest of the stuff I’ve read about s4, though, sounds promising.)
