First off then, episode thoughts:

That was an interesting episode. It started off fairly obviously going down the light-hearted silliness route, and I thought it was going to be just an okay episode, and was a bit disappointed they'd left out some last season's character development.

But the it got a bit further in, and when Pinkie started to get a bit shaken by what was going on, it moved a bit further into not-quite-fridge-horror. The mirror clearly only makes things that are imperfect copies - the impression I got was they were mentally a lot simpler, both in terms of retained memories and a charactured personality. (One wonders if the mood the user is in when they made the first copy has anything to do with it.) Though the copies themselves don't appear to suffer from any noticable replicative fading. It also gave Pinkie a solid glance at what she's like from other people's view, and it seemed to rattle her a bit. And the impeding danger of her own... death? Erasure? Was a little bit creepy. (I wouldn't be at all surprised if, before long, we see someone explore what happened if they did send the real Pinkie into the mirror.)

Overall, a fairly average, fluffy episode, but one that nonetheless managed to show that Pinkie, while still being physics-defying Pinkie (that slows fall into water; she is totally a psion, I swear) but that, at the end of the day, she has grown a bit since the start of the show.

Incidently, was that Fancy Pants in the Ponyville crowd, whose hat a Pinkie jumped out of?

Also, Spike locates the day-saving-book... Stepping up his game this season, ain't he?

Angry Fluttershy - scary! (Well, relatively speaking...)

This also seems to indicate there's no overarching story to this season, though I'm still hedging my bets we may not have seen the last of Sombra1.)

Right, back through the thread, and then maybe a report from Princess C...

1In case you're wondering why I haven't reviewed that second Sombra story you guys linked, it's very simple; as it concentrated solely on the OC, it never actually got as far as saying anything about Sombra, and it was sufficiently purple-prose dull I wasn't going to subscribe to more of that bilge, and it didn't give me enough to work with. (I'll still count it towards the total, though. Which is, to my great surprise, still only two, 6/14 days in.)