As Season 9 marks the end of a groundbreaking generation of MLP, certain questions will be raised or remain, as I highly doubt that the show will address everything at once. For me, it is: what will become of Limestone and Marble Pie, the other Pie sisters?
These two were interchangeable in the 1st season as fillies, and even though they were eventually given their own personalities, they still tend to be mentioned collectively. The MLP wiki didn't even give them separate pages. That may be because they were backburned by Maud Pie, a character whom the audience was supposed to pretend that she grew up with Pinkie, Limestone, and Marble on the rock farm, even though she was MIA in "Cutie Mark Chronicles." Maud Pie is a unique character in her own right and a welcome addition to the series, but she conspicuously overshadowed the two sisters we've known longer.
As the series continues from "Hearthbreakers" onward, Limestone and Marble have become more layered characters, adding interesting details that I would not expect to see from them. For Limestone, I was turned off by her hostile behavior and bad attitude. But her actions are not without reason. She is essentially the leader de facto of the rock farm and is tasked with the important objective of guarding Holder's Boulder. I bet Limestone's dealt with quite a few threats to the boulder. She also suffers from misery, which may be due to spending her life on a rock farm, and has jealousy issues. Despite her flaws, she has some sage advice for Pinkie in "The Maud Couple," explaining to her that even if you may not understand someone, if someone you love understands said person, that's all that matters.
I initially dismissed Marble Pie as a moeblob who was seemingly created just to be a potential love interest for Big Mac. Personality and character development seemed irrelevant; if a character could make some cute, shy faces and squeak, bronies would be all over that sh*t. I thought it was ridiculous that Marble Pie won a big poll for best Pie sister.
Eventually, I gave in to her cuteness, especially as Fluttershy grows more assertive and less, well, shy, making Marble the go-to shrinking violet of the show. I love her color palette and her mane. I also love how she can speak so much without saying a word. In "Maud Couple," it was unexpected when she shot her rude sister Limestone a dirty look and managed to convince her to solve Pinkie's issues with Mudbriar without saying a word. She can say, "I can't believe Pinkie Pie and I are sisters," "Limestone, that wasn't very nice," or "I'm listening." She's essentially the Silent Bob of the MLP universe.
Silent Bob's been chasing Amy. Likewise, Marble Pie may be chasing Big Macintosh. Her little ship tease with the big guy never panned out for whatever reason, and I thought the staff would pretend MarbleMac never existed. In the SugarMac episodes, Marble was not mentioned, not even as a first crush. But then, "Best Gift Ever" happened. It only lasted for a couple seconds and may be easily missed, but Marble Pie's heart was shattered that day. It was a powerful image for those who caught it, and reactions were all over the place. Some felt the scene built sympathy and relatability to the character. Some felt it was a slap in the face to MarbleMac shippers. Some fans felt Marble should've reached out to Big Mac more. Others brought up the, "Are the Apples and Pies related?" argument. But what most would agree on was that it was painful for Marble Pie and the audience. Regardless of the scene's intentions, it's laid the groundwork for an interesting concept: Marble Pie dealing with her unrequited love, moving on, and finding somepony else to love. I say unrequited because Sugar Belle was deemed Big Mac's first crush, implying that Marble had feelings for him the entire time that he never reciprocated. Ouch. It was that episode that solidified my love for the youngest Pie sister.
Limestone and Marble are two characters who have grown on me over the course of the series. With Limestone's jealousy and Marble's heartbreak, a potential episode exploring possible romances for the two would likely give them a much deserved happy ending. And even if their romantic desires had been fulfilled prior to season 9, I would love to see them play off one another and find a way to escape the drudgery of working in a rock farm. Thankfully, them receiving additional exposure on the show is granted, evidenced by them and Maud playing a small, but pivotal role in Pinkie's story in "Best Gift Ever" like in "The Maud Couple." They even teased Marble speaking! I don't doubt they will make an appearance in Season 9, even if it is for the sole purpose of Marble saying something punchy, but a starring role for the two is uncertain, as countless plot threads, settings, characters, etc. vie for a role in the spotlight. But Season 9 may be the one that will go all out, so nothing is entirely ruled out. This could be the season which puts them at equal importance with Maud Pie, and if not, still ensures they are well-developed, much appreciated characters.