Of all the episodes in the first half of this season, the two I had been most looking forward to were the one where we met Rainbow Dash's parents and this one, which focuses on Celestia and Luna, with Starlight Glimmer too.
(spoilers)
The episode starts right away with two big firsts for the Cutie Map: Starlight Glimmer becomes the first non-Main 6 pony called by the map, and also the first one to be called on a completely solo mission.
Starlight goes to Canterlot and quickly realizes the friendship problem is between none other than Celestia and Luna. Knowing that she has to carefully consider her actions with the royal sisters themselves, she starts by simply observing a typical day in their lives, and realizes the problem is that they are both unintentionally hurting each other's feelings because they don't really understand how much hard work the other has to go through. Starlight's first decision is to simply mention the problem to both of them and let them talk it out. However, they quickly descend into arguing, and in a desperate attempt to get them to stop fighting, Starlight ends up casting a spell that swaps their cutie marks. The spell lasts only 24 hours, but cannot be reversed, not even by Starlight, so now Celestia and Luna are forced to spend the day doing each other's jobs.
Luna tries to go through the day in Celestia's place, and after a lot of forced smiling, an ill-timed photo with some foals, a poor choice of words with some visitors, and a three-hour debate between two city mayors, she is understandably exhausted at the end of the day. When it's Celestia's turn to go through a night in Luna's place, she not only has to deal with the complete loneliness, but also has to help Starlight through a nightmare in which Luna and Celestia's bickering has turned them into their evil forms, Nightmare Moon and Daybreaker respectively. Celestia pulls Luna out of her own nightmare, and although only Luna's magic (now possessed by Celestia) will work in the dream realm, they both talk it out and reconcile with a better appreciation for what they both do, allowing Celestia to have the strength beat back the evil royal sisters in Starlight's nightmare. As the sun rises the next day, the 24-hour limit arrives and their cutie marks automatically switch back to where they belong, and Starlight receives the signal that her friendship mission has been successfully completed.
Like I said, this was one of the two episodes of the first half of Season 7 I had been really looking forward to, and it did not disappoint. Not only did we finally get that Celestia episode we had always wanted, but we also got a surprise glimpse at (supposedly and potentially) Celestia's evil form, Daybreaker. In fact, out of all the spoilers resulting from the early Canadian releases, Daybreaker was by far the most difficult one to avoid because she was just that immensely popular. Now that this episode has finally aired in the US, I expect the floodgates of fanwork to really open.
(end spoilers)
One more episode left to go, then it'll be on to the three Equestria Girls specials.
