Limestones smirk.

When you think of it…  

Shrug, and say “when in Rome…”

@ghostfacekiller39  
She’s deliciously sadistic and I like it!

Won’t lie, I unironically find Limestone’s expression here cute
 
It’s just got that weird psycho thing going on and it’s fun

@zerowinger66  
ME TOO! HOLY SMOKES SOMEONE MAKE THAT! :O

@AaronMk  
Don’t be surprised if some folks like that. :(

Awkwardly smile from the realization that any one of these ponies could bust my ribs without even trying. Also watch what I say, and do, and think.

@Somber Star  
Some people think that “trying too hard” makes for humor.

@Brony_Conundrum  
The hell did she do to you?

Take comfort in the knowledge that I spiked Limestone’s soup with a triple dose of laxative. Then act all innocent when she jumps up and charges upstairs, and keep a demure little smile while the rest of the family awkwardly tries to ignore the agonised cries from the bathroom for the next fifteen minutes or so.

@Background Pony #9687  
Of course she’s the favorite. She’s the one getting a degree without breaking family values.

@toonbat  
Because Aparently She’s the favorite Sister.

Limestone is just happy to see that you like the soup, as is the rest of the family. Prolonged exposure to rocks just made them bad at expressing it.

@Sum Ergo Cogito  
I absolutely love the idea of a bunch of crazies that worship the V8 engine.
 
WITNESS ME!

Immediately check my soup for poison.
 
And my rock for laxatives.

Heeeey! Why does Maud get a pumpkin on her soup?

@Derplicious  
Wait, waaa, I don’t even… too MUCH Mad Max? That makes no sense; that’s just random letters.
 
Oh well, back to Fury Road.
 

 
V8! V8! V8! V8! V8!

Immediately start noping after seeing Limestone’s expression.

@edvd
 
And I don’t know if it’s just the eye designs, but she seems far sadder than Fluttershy. Like a deep sadness.

@Somber Star
 
Not sure about the others, but Marble’s anxiety is probably worse since she can’t even get a word out.

@TheAntiCat  
All 4 of the Pie girls are crazy. Probably that repressive traditionalist upbringing that would be extremely religious if Equestria were afflicted with such a thing.
 
Limestone: Highly aggressive, bipolar minus the requisite other pole.
 
Maud: Obsessive, with high-functioning autistic tendencies (such as expressive and emotional read deficiencies).
 
Pinkie: Bipolar. Paranoid schizophrenic. Emotional dependency. Also traits of escapism. Ironically potentially the most sane and stable of the four.
 
Marble: Social anxiety disorder competitive with Fluttershy’s.

….I’ve been watching too much Mad Max.
 
I though Pinkies mom had Immortan Joe’s gas mask on her, when seeing the thumbnail.

Something tells me that some of Limestone’s marbles fell to her younger sister.
 
What I’m saying is, she’s fucking crazy.

@Kamazeustra
 
No worries, I experienced major cognitive dissonance upon meeting adult!Limestone myself.
 
When we first saw Limestone in Cutie Mark Chronicles, she had a perfect bowl cut, implying a waifish demeanor (which Marble got instead).