"I mean... what I'm saying makes sense right? You get where I'm coming from don't you? It's so obvious! I can't believe I didn't see it before and I can't believe you're skeptical about it!" Twilight proclaimed, she had just dropped a bombshell of a conspiracy theory but Fluttershy was extremely doubtful of the claim, how could Sweetie Belle be Rarity's daughter?
Fluttershy went "Geez, I don't know Twilight, I mean... Sweetie Belle being Rarity's daughter? I know they're pretty similar but they're just like any other sisters, don't you think ponies would have known that they were mother and daughter by now?"
Twilight rolled her eyes and went "Well DUH! Rarity doesn't want ponies to know! Having sex and also having a child out of wedlock? It would ruin her image! She's a high class pony!"
Fluttershy nodded and said "OK... but how do you explain her parents then? Did Rarity bring Sweetie Belle home saying she was an orphan and they just adopted her or something?"
Twilight scoffed as she said "Of course not! They must be lying for Rarity's sake but are trying to force Rarity into motherhood! It's the only thing that makes sense!"
Fluttershy, still unsure, stated "Alright, present a case for your conspiracy theory and then I'll point out the flaws, if at the end of it I believe that your argument is even remotely believable... I'll post it anonymously on a conspiracy theory blog, if not... then you'll have to feed Angel"
Twilight raised her eyebrow as she asked "The forfeit is feeding your rabbit?"
Fluttershy nodded and replied "Uh-huh, he's a fussy eater! Go ahead, provide your evidence!"
Twilight grinned and prepared to detail everything that had led her to the conclusion that Sweetie Belle was Rarity's daughter.
"To start with, let's focus on the first thing you mentioned, Rarity's parents. I don't care who you are or what your situation is but most parents do not normally just ditch their own kids to live with their big sister! Good parents don't do that and from what I know, Rarity's parents are very nice ponies, they've no reason to just dump Sweetie Belle onto Rarity and say "take care of your sister, we can't be bothered and we hate her, bye!" While we are on the subject of Rarity's parents, have you noticed that Rarity always speaks really posh while her parents are... let's say not-so-posh when they talk? That doesn't just happen, Rarity has made an effort to distance herself from her parents, why? Probably a theory for another day but it's a strange coincidence that Sweetie Belle takes after Rarity in terms of her voice, not to mention looks! I know siblings can look similar, like Aloe and Lotus or Flim and Flam, though other than those four can you name me any siblings in Equestria that look even remotely similar? Think about your own brother for instance! You could say that it's not a fair comparison because of gender but all you have to do is look at Applejack and Applebloom, they don't look anything alike! I think Rarity's parents forced Rarity to take Sweetie Belle in so she could be a real mother, Sweetie Belle clearly adores Rarity but Rarity often wants nothing to do with her because she knows that if the truth came out it might damage her fancy facade! Also, between you and me, those two have a dynamic that is way more like a mother and daughter than two sisters, wouldn't you agree? It just makes sense, right? There you have it Fluttershy! Three big main points of evidence, Sweetie Belle is Rarity's daughter!"
Fluttershy considered Twilight's points and said "Well... the point you made about her parents is a decent deduction, I don't think I've ever seen pony parents who were so terrible as to foist their own daughter onto their other daughter, so that can't be it. The likeness? Again, I can't exactly fault you on that, they look way too similar to be sisters and to be fair, they don't look similar enough to be twins... also they don't share too many similarities to their "parents" and as for their strange sister dynamic seeming more like a mother/daughter dynamic? To be honest Twilight... I got nothing, I can't argue with any of the points you've made apart from the fact that Rarity has inherited skin color and mane color from her parents while Sweetie Belle only inherited skin color which she could have easily got from Rarity assuming your theory is correct... though on that point, if Rarity is Sweetie Belle's mom... then who is the dad?"
Twilight bit her lip and said "That... is something that I don't have the answer to unfortunately, though everything else lines up doesn't it? I'd say my strongest evidence is eye color! Rarity's parents both have blue eyes, Rarity has blue eyes but Sweetie Belle miraculously has green eyes? Highly suspicious! There is a green-eyed stallion out there who's a dad and probably doesn't even know it!"
Fluttershy nodded "Yeah Twilight, I gotta admit you're making a lot of sense here, you're conspiracy theory isn't perfect but let's face it, what conspiracy theory is perfect? It's posted!"