"''Tis about time'?"
"And a good evening to you, sister." Luna kept her focus on raising the moon. After all the activity the sun had seen today, her own charge was sulking a bit.
"What exactly was that supposed to mean?" said Celestia, who from the sound of it had forgotten that her royal title was a thing of the admittedly recent past. Granted, they were still quartered in the palace, but Luna gave that another generation at most before they were politely asked to leave.
"You will need to be more specific." There. The petulant little attention horse was thoroughly placated, assured it was just as important as the sun, and set on its course. Honestly, Luna didn't know where it had learned that kind of behavior. "There are times for many things. A time for Neighsay to retire, a time to relax nighttime noise pollution statutes, a—"
"I think you know what I mean."
Luna rolled her eyes. That tone hadn't worked on her for more than a millennium. All those students must have preserved the habit. As she turned to face Celestia, she said, "Clearly I do not, or I would have answered your question by now."
The attempt to loom over her was similarly out of date. "A certain emergency Spike warned you about?"
"Ah, yes, your human counterpart." Luna took a few steps back to better give her sister a flat look. "Good to see someone take a stand against irrelevance."
Celestia drew back as though struck. "Excuse me?"
"Sister, from the moment we returned from our post-abdication vacation, neigh, even during it, you have moaned and whinged about having no purpose left in your life. Never mind how this is the end result of a scheme you put into place, it is clearly the worst thing to ever befall you. Despite the fact that these are circumstances of your own making, you, o queen of wheels within wheels, made no plans for yourself after you gave Twilight the throne. And it seems your answer to that crushing ennui was to do what you have done for literal centuries, save you did it in another world."
Neither said anything for a time. Finally, Celestia sighed. "Not my finest moment, no. Though in my defense, Grogar—"
"Aye, the goat carries some blame, but not all. I said 'twas about time not only to see the power of the sun brought to bear in a way that does not glass the countryside, but that a Celestia actually left her comfort zone, to use the modern term." Luna gave a wry smirk. "You could learn from yourself, Tia."
"I've already learned much today..." Celestia turned away. "Though I suppose lessons never truly end."
Luna wrapped Celestia in a hug. "Was it not our teacher who said only the dead stop learning? Come, dearest sister, tell me of your travails in the shimmering lands of humanity. I would know of yon faculty lot and the dread power it contains."