Overall episode thoughts
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A pretty good episode overall. The premise and lesson were solid and we see that Pinkie has more depth to her than her silliness. There were also some hints of party of one here as Pinkie didn't go crazy this time but did get really depressed when she realized that she had done something to make her friends unhappy.

Hidden library compartment seems like it will spawn many fanfiction ideas.

I would have liked to see some more differentiation amongst the clones. They were more of a single Pinkie whirlwind phenomena, but they could have all had different toys or musical instruments in a scene, for example. I think something like that would have been a good scene, this one was more like a generic plague of locusts that happened to look like Pinkie.

When it comes to boring, Twilight Sparkle is truly the best there is.