Ever since the Season 4 trailer came up, everyone has been wondering how Nightmare Moon is returning. Why is Luna allowing it? And what does Twilight (Yes I'll call her that for this blog) have to do with it? Well the answer is simple: Its only a flashback.
First sign is that Luna doesn't call Twilight by her name. Second, Luna is talking to Twilight saying that she is jealous of people basking in her light, meaning that Twilight is seeing this in Celestia's point of view 1000 years ago. Third, and most importantly, this is Luna we are talking about! I am 100% sure that the writers would know not to have her become a villain again. Not only is she a major fan favorite, but this anger and jealousy is not like her in anyway.
So yeah, to me, its only a flashback. What are your thoughts or theories on this? Leave your comments down below.