Some might be confused as to why Rarity's "Gaze upon my gems!" line is randomly in the intro when nobody else speaks. This might be because if you noticed, there was no "it's a posh life" at the beginning to describe her, while everyone else's descriptor got mentioned. Her line comes right before "it's a fun life" and after "it's a fast life", and if you re-listen to the Theme Tune Roll Call at the end, the placement of the line starts to make a lot more sense.
Why is Applejack now suddenly the Fourth-Wall Observer in this show? Well besides the fact that it's a reboot and they need to repurpose the Mane 6 to spice it up a bit, it makes sense that AJ would talk to the audience and be aware of what's going on considering she's the element of honesty. She's known for being honest, so she's honestly aware of the fact that she's in a cartoon.
An alternate reason is that in the normal, (relatively) down-to-earth world of FiM it was the wacky, outlandish Pinkie Pie who often broke the fourth wall; therefore in the wacky, outlandish world of Pony Life it is the normal, down-to-earth Applejack who gains this awareness, while Pinkie simply goes with the flow.
There's precedent. She had one of FiM's most self-aware lines: "We don't normally wear clothes."
The way that the Mane 6 keep wanting to drink potions, and are completely dependent on Potion Nova to provide them, looks suspiciously like drug addicts getting their fix from a dealer.
Well into the series, we then find out the Mane 6 are completely unaware that Potion Nova is restocking their potion cabinet, and they want to catch her breaking in to do it, but fail. So these ponies aren't being dealt basically drugs, they're being forced to have them around. And potions have been shown to be dangerous, with it being possible to easily get accidentally trapped inside a bottle.
BigHoof is out there, looks more terrifying than anything else in the show, and the ponies are completely unaware.
Pinkie's line about missing her brother may at first sound like he got lost, but given the story she begins to tell seems to be Hansel & Gretel, implies he was eaten by a witch, assuming he wasn't Octavio in a case of Unexplained Recovery.
Bubbles is seen floating helpless in the Cute Triangle, "where everything lost is lost forever". This is the first time we see him after he blasts off in Cute-Pocalypse Meow.
Even if the cookies that came alive didn't fall apart in the rain, they're completely unprepared to deal with, well, anything, and in a society of ponies that eat almost nothing but sweets. These were basically Pinkie's children, as well.
When AJ tells an apple how much she loves it, it comes alive and giggles. It doesn't turn back to normal after things change back to reality, suggesting it really is alive just like Pinkie's cookies. This suggests food comes alive if you treat it like it's alive, and thus Sapient Eat Sapient likely happening accidentally on a regular basis.
In a world where many animal species, even cats, can talk, and all non-insects at least seem to be sapient, the ponies are familiar with the meaning of "meatballs".
