I have to say, what I was most nervous about this episode was the idea that Pinkie Pie would come off as too obnoxious. And while it IS true that the main conflict of the episode is the fact that all those Pinkie Pies will get on everypony's nerves, it actually works. They made it clear that the Pinkie Pie clones aren't the same Pinkie Pie. Not only do they not have the same memories as the original Pinkie Pie, but they also don't have the same kind of restraints or attachments the original Pinkie Pie has. The Pinkie clones are all about fun, usually at the expense of everypony else. They can be pretty thoughtless, whereas the real Pinkie Pie realizes what a mess she's gotten herself into. In fact, it's funny to see that the original Pinkie Pie is the one that's mopey and concerned for everypony else. I like that, it's kind of a redemption for how she acted in A Friend in Deed... Or maybe it's because of A Friend in Deed that she's more considerate.
I also have to admit, when it comes to the "which is the real one" scenarios, I'm always nervous, since the show might throw a twist that the real one was actually destroyed with most of the copies. Hell, I'm still not entirely sure that the one left afterward is the real one, for all we know it could be one of the clones smart enough or patient enough to not fall for Rainbow Dash's balloon animal trap. But then again, the episode went to pretty great lengths to show that the real Pinkie Pie cares more about her friends then having fun, and that the rest of the Pinkie Pie clones literally don't have any self control whatsoever. Still, I always find myself second-guessing...
That book Spike found... That HAS to be important. I'm not saying that as a guess or a theory, I'm outright telling the writers this. You can't have something that's hidden away like that just as a throw-away thing to help Twilight out in this one episode. Not to mention, did they really need to make it so that Twilight didn't know anything about the Mirror Pond? If the book isn't going to be important, then why even bother having it hidden and making it so that Twilight was clueless in the first place? I also don't like how the book looks utterly generic, like you can look like any other book. I expect a book hidden away like that to have SOMETHING distinguishing about it.
Animation good as always, Pinkie Pie was extra cute in this episode... I liked the part where Fluttershy helped Pinkie Pie calm down with her butterflies! X3
Some other highlights:
-Those two other apple family members trying to raise the barn... I'm sure they were mentioned in the first episode, but could someone say who they were? Maybe they're early for the family reunion...
-Fancy Pants cameo. Wonder what he's doing in Ponyville... and with that hat.
-G3 Pinkie face... Would have been more awesome if the Hub didn't already spoil that in the ads for this episode... Also, they edited it for the commercial; she was doing in to Fluttershy and Rarity in the commercial, but to another Pinkie Pie in the episode proper.
-Orange Frog... I wonder if that's going to be like Blinky, the three-eyed fish from The Simpsons, and we're just going to randomly see it every now and again.
-Paint drying... Surprisingly intense. Reminds me of that one episode of The Grim Adventures of Billy & Mandy, where Billy was watching paint dry...
-Big Mac, Applejack, Apple Bloom, and Winona all gathering the Pinkie Pies, it was awesome.
-The Pinkie Pies themselves were cute, the way they bounce around, dancing, saying "Fun" all the time! :P
-Pinkie clone growing fingers... That's some *bleep* I'd expect from HotDiggedyDemon, yet here it is, in an actual episode of the show. If people though G3 Pinkie face was creepy, THIS... I don't even know where to begin!