@Background Pony #291A
 
@Background Pony #9D0B  
Yes, the series not end, we didn’t see Sunset and H Twilight,so more Applejack mermaid comming.
 
Ah! I uploaded a new pic form PhysicRodrigo, for now no more pics.

@Background Pony #9D0B  
||Yet later panels revealed the side effect was inevitable. The right mindset only accelerated the effect, but it would happen in a matter of hours even if their minds were left alone. Applejack and Fluttershy proved this by being at opposite ends of the spectrum.
 
I ultimately think the entire thing was pulled out of the blue, and may not even have been the intent when this series started. It may have come to his mind when Rare showed up. I think out of all of them, this would upset AJ, RD, and Rare the most. If it’s ever touched upon in comic, I see these three being the most actively are of it.
 
I mean, look at AJ. She’s totally loving this. Like she’s thinking, “Damn, I sure am sexy like this. Yet, I’d like to have legs anyway. Least these clothes bring as close to normal as possible while this curse is in effect.”
 
I also think it may be yet another manner of spreading the curse. Had AJ been wearing a full on dress like Pinkie, Fluttershy, and Rarity, as opposed to the miniskirt she, RD and Princess Twi had, the next victim wouldn’t have caught it, unless she was deliberately trying to turn herself. ||
 
Fortunately, it’s not permanent, and after two or three days, they may do as they wish again, and you know AJ, RD, and Rare will take full advantage.

@Background Pony #291A  
It’s like you said. The combination of her fish tail, outfit, and the setting (her sitting on that bench) pretty much made this the best pic of the series so far.
 
Yeah, I don’t know why he introduced that side effect. Comments on DeviantArt claim it has to do with how much their subconscious has accepted their finny fate, but I partly think it’s just a deus ex machina to simply expunge the clothes and place them in seashell bras. I still think it showed more originality when they had their clothes intact.

@Background Pony #9D0B  
Agreed. Applejack is so attractive looking with a fish tail and clothes on here.
 
Such a shame there is another side effect yet to be revealed at this point, and I suspect you know what it is.

@Background Pony #291A  
I figure about that first part, those “parts” most likely hide under a seamless flap or panel of skin and scales, probably slitted or Y-shaped, and when not in use & sealed is wholly indistinguishable from the rest of the tail as to not draw attention to them.
 
Because of their ability to stay out of the water as long as they wish, I actually kinda hope Physic decides to conclude the story with Applejack and/or Pinkie still a mermaid, preferably Applejack, because as you see here in this pic with her fully dressed on that bench, she can TOTALLY rock the fish tail, and her skirt on top of it makes her look even cuter to boot!!

You know, I actually wondered about this. Does AJ still have her best parts? Do the others still have their best bits after becoming merfolk? And if a man got it, would he still have his? If not, that’s another form of nightmare fuel, even worse than losing your legs.
 
At least on those grounds, you get a nice, thick, long, powerful tail which has its own advantages. Plus, like Spolsh, Pinkie and AJ can continue their lives as usual with accommodations should this prove to be permanent. The others have no such luxury given their gills make them more fish-like, confining them to aquatic environments. Twilight, Rare, RD, and soon to be Fluttershy cannot leave the water as they please once they became mermaids. AJ and Pinkie are more like sea-lions than fish.
 
There’d be no substitute for your most favored organs.