Just want to offer my full thoughts on Princess Flurry Heart, who is surprisingly not being discussed as much as I would have originally thought.

First off, the books are considered canon by many now more than ever, because all of the writers of the books have now written for the show, and the books are officially licensed. Stories made by people who work for the show count as canon.

That said, here goes the main arguments.

1) The show makes it very clear that Alicorns are supposed to be special. It's complete and utter break of continuity if too many Alicorns join the cast. If everyone is special, nobody is.

2) There are indeed two kinds of Alicorns, born and ascended. That's why I stopped complaining about that aspect. But, it is worth noting that most of the Alicorn tribe vanished (source: Book of Two Sisters, written by show staff).

3) However, the show makes it clear that the Two Sisters, Twilight, and Cadence are special even among Alicorns. The first 3 are connected to the Tree of Harmony, and Cadence to the Crystal Heart. Those 4 are special even among Alicorns. So, Flurry Heart should not be on their level. And giving her some grand destiny is a major risk to telling a good story. More on that later.

4) Born Alicorns are a thing, but the fact that she is a special Princess without earning the title puts her in a different status from the other 4 Princesses. Celestia and Luna had to prove themselves to the population of Equestria, even though they were elected into power by a council solely because of their Alicornness. The population was not completely in support, so they had to prove their right to rule over all ponies by uniting Equestria. Cadence saved the villlage by fixing the Crystal Heart Spell. Twilight mastered the Magic of Friendship. All of them did things before earning the full title of Princess of Equestria.

5) The earned title of the 4 Princesses was a major part of the show's intended feministic message. That females can earn powerful positions with hard work and determination. Strong females. Flurry Fart was born a Princess, which cheapens that message.

6) There are several issues related not only to her Alicorn and Princess status, but here status as a "special" baby. "Special" babies are notorious for being walking plot devices. If they don't give her any significant power, then this will be headed off. But if she is "special" and powerful, the risk for bad writing skyrockets.

7) If I were to use the example of Poof from Fairly OddParents, Poof was a MacGuffin and Deus Ex Machina at the same time. He was a walking plot device, existing only to serve as both conflicts and solutions. Given the general difficulty of writing a baby (since how deep and interesting can the character of a baby be?) it is all too easy for them to become a mechanic, rather than a character.

8) Further, if they do something stupid like a "Chosen One" type of story- not only has that been done already in this show- but it is an overused trope. And it's all the worse if you have a baby be the "special" character. Because a baby, lacking in reason or autonomy, can only be shallow. And if they make the baby smart, and/or powerful, it changes them into a character, sure. But that kind of OPness and Precociousness makes them a borderline Mary Sue/Gary Stu on TOP of being a walking plot device.

9) Babies are one of the worst characters to add to a show, and are notoriously easy to mess up. If she isn't special or powerful, then fair enough. Flurry Heart would then be in the same class as Cadence and Shining- just kind of there. But if she is made special and/or powerful, it would be horrible.

10) Regardless of whether she is special or not, the chances of her being anything other than a stupid plot device is very low. In all likelihood, she'll be more of an object than a character.

11) Underneath it all, it can't be forgotten that a historically bad character type was forced into the show by a toy company that cares about profits way more than writing a cohesive story. No sane writer would add one of the worst archetypes to a show if they weren't forced to. Babies are an inherently easy character to mess up, because their inferior capacities make them an object, and not a character. And adding higher capacities makes them OP and boring instead of a walking plot device. There are two extreme sides of adding a baby to a show, and very little middle ground

So, there are all the reasons it can go wrong, or is perceived as a major threat to the quality of the show. That said, let me preemptively state some solid counterarguments.

It could be said that the writers are very capable, and indeed they are. They have taken plenty of lemons from Hasbro and made them something cool or interesting. However, it is verrry hard to fix babies.

It could be said that the books are only semi-canon, and I want to say no to this. I don't think something officially sanctioned, and officially written by the writers is anything other than canon.

It could be said that Flurry Fart being a walking plot device is no different from Cadence or Shining, and a couple of other characters, and to be fair, that's right. However, that doesn't mean it is excusable to add ANOTHER boring MacGuffin/Deus Ex Machina, who, if done wrong, might ALSO be a Mary Sue.

It could be said that maybe MLP isn't intended to be feministic anymore, and that it has deviated from the original path, but I disagree. Because, even as recently as Season 5, we saw plenty of cases where the strength of the main cast as self-made, independent females, was made very clear. And even if that is not the direct intention anymore, having even one character that breaks the mold of strong females is definitely a disconnect from some of the feel of the show, which features many strong female characters that do things to show their strength, ability, and they earn their achievements. Making being born an achievement is a disconnect.

It's obvious to say that I am jumping to conclusions about her being "special" and that I should wait until the episode actually comes out. But, don't forget that Alicorns are by definition "special" in the world of MLP. So, that's very much a given conclusion. The odds of her being normal are outweighed by the chance she'll be a special snowflake. The show itself makes it very clear that Alicorn = Special. Even though making her normal would help the situation, this is objectively a break in continuity. Nobody will deny that the show itself is canon.

Believe me, I would love if she is just a normal pony. That would stop her from being a Mary Sue, at least. That would actually make an interesting notion that the 4 Princesses > normal alicorns > normal ponies. Which is an interesting power dynamic. It would also make for some Alicorn lore, and more specialness to the main 4 Princesses. And also that Alicorns aren't inherently powerful. Which is definitely one of the better ways they can handle this. But will the writers make her normal? Time will tell. It would still be a contradiction to the existing story, but it would be better than having an OP special snowflake baby.

Tangentially related, but not really- Mane 6 as Alicorns would be cruddy for different reasons. It would make it a bit more boring if they all had the same abilities. Putting them in the middle ground or normal alicorns > normal ponies would be a disservice to their importance, but making them all on the same level as the 4 Princesses would be boring. Also, that would make Alicornness TOO normal. I like the idea of "normal" Alicorns, but seeing a bunch of them, and seeing everybody attain that just gets rid of diversity, and makes things flat. There should be such a thing as "special". Because if nobody is above the rest, then it becomes washed out.

At first that may seem contradictory, but the short way of saying it is this. There should be "special" characters. But that specialness should be earned, not given. Also, if too many people are special, nobody will be, hence having an entire cast of "special" characters (ascended alicorns) would cheapen the value of that gain.

It can be said that MLP was created to sell toys, but it should be subtle, and it isn't good if the story we love is harmed by MLPs status as a toy commercial. The writers chose to make a good show, and when Hasbro makes an executive decision in affront to the canon, it is infuriating. Just a reminder that they only care about their bottom line, breaking through the 4th wall without a care. When stuff like this happens, it snaps the viewer back to reality, saying "That doesn't fit! HASBROOOOO!"

That's what I can think of in terms of direct responses to my points

Now, how can the baby be done as well as possible? (in order of preference)
1) The Changeling theory is fascinating and would actually be amazing. But I doubt it

2) She is disabled/deformed and she can't fly or use magic or something like that. This gives her flaws. If her power is negated in this way, it's an interesting way to use her. The only exception is I don't want a darn dumbo story where the only thing she has to worry about is bullies. Bullying has been done very well in this show already. Don't need to cover it anymore.

3) She is some kind of omen. Not my favorite choice, but if it's something where she is barely featured, then I don't mind much.

4) She is just a normal pony. Nothing special about her, and she's just there. This makes her no better or worse than Cadence and Shining in their first appearances.

5) Don't feature her like, at all, outside of these two episodes

Stories I DON'T want.
1) Chosen One BS

2) As powerful as the Princesses

3) Poof-format stories where she goofs stuff up only for everyone else to clean it up

4) Kidnapping. Unless it is related to the changeling story possibility mentioned above.

5) The only conflict is dealing with a "special" baby that is harder to take care of than normal babies

6) Dumbo/bullying type of story

Anyways, that is a big read, I know, but please do.

Also, I should point out that her eyes being bigger is just the new Foal model. If you remember the Pinkie Pie episode, AJ had this eye style in her baby picture as well.