(spoilers)
This was a rather mixed episode for me. I really liked how we got some real backstory on both Applejack and Big Mac, but I also kept cringing at young Applejack's series of lies growing increasingly out of control (though I suppose it's understandable why Applejack herself says that she isn't proud of what happened that day).
To give some context of how far back those events took place, Filthy Rich had been only engaged to Spoiled Rich (named Spoiled Milk at the time). If we assume Diamond Tiara and Apple Bloom to be the same age, then that confirms Applejack's parents were still alive at the time, which makes their absence in this episode rather curious.
It's actually rather complicated how the events of this episode unfolded. Applejack wants to be the one to one day take over the farm and has plenty of big ideas, while Big Mag frequently disagrees. With Filthy Rich now taking over his family store, Applejack wants to prove her capability, so she makes a promise for selling cider in the store, but Granny Smith won't allow it, forcing Applejack to go back on her promise. Filthy Rich threatens to cut off business ties (which would ruin the farm) if Applejack goes back on her word, which makes her lie about Granny Smith being sick. One thing leads to another as Applejack and Big Mac struggle to keep Granny Smith and the Rich couple away from each other, leading to all of them visiting the hospital, and it is when Granny Smith is about to unknowingly hack off one of Big Mac's legs that Applejack finally confesses to her series of lies.
I was pleasantly surprised that this episode explains not only why Applejack is so honest, but also why Big Mac hardly ever talks. Big Mac used to be very talkative, practically saying everything except eyup or nope. And while Applejack learned how a simple lie could send things spiraling out of control, Big Mac learned that he could avoid a lot of problems if he simply listened to others instead of talking all the time.
I also noticed how almost everypony looked slightly younger during the flashback. Applejack was no longer a small filly but not quite an adult, Big Mac was a little smaller, and even Granny Smith had a slightly younger appearance. This was also seen in the background a bit too, such as Cheerilee in her "teenage appearance" seen way back in Season 1's "Call of the Cutie", and we even saw Derpy at the hospital with bandages over her eyes (I think we all know what might be the reason for that).
With the amount of backstory revealed in this episode, I will say that this was definitely worth watching, despite its crazy moments.
(end spoilers)
Like I said earlier, I'll give my thoughts on the remaining episodes when they air in the US over the next two weeks, as usual.
