@Millennial Dan
 
“There are exactly four alicorns so far, all with varying shapes and sizes”
 
And ages, which is exactly why I’m basing it on. If they keep growing, that is exactly what you would expect, meanwhile most adult ponies follow a standard model.
 
I’m not saying I know better, and we know so little about Alicorns that almost nothing about them and their life cycle is set in stone. However even if one hadn’t assumed that being Alicorns had much to do with Celestia, Cadance and Luna’s height/horn size/body type before, the fact that they showed those exact effects starting on Twilight seems like confirmation that the staff sees it as race-tied traits.
 
Only time will tell if we’ll get to see Twi looking more like the other Princesses. I think it would be a very cool visual progression and one that would make sense with what we know. Who knows? We might even learn more about the alicorn race in future episodes or movies.

@Background Pony #16C6  
There are exactly four alicorns so far, all with varying shapes and sizes. We can agree that their size increases at least once in the process of becoming an alicorn, but anything else is purely hypothetical.

@Millennial Dan
 
We don’t know how old Cadence was in the flashback, but she didn’t just grow to a regular mare’s size and body type, she changed very clearly.
 
How long do Alicorns grow? We do not know. We know nothing much about Alicorns. But I’m pretty sure that Celestia’s unique age has to do with her unique height and body. And I’m pretty sure Twilight still has a way to go before she grows fully into her role, but the very fact that her body already changed in a simmilar way should tell you something.
 
Why are you against this anyway? Pretty much everyone agrees that Alicorns are tall and lanky, it’s just a fact at this point. Alicorns also seem to have have a different life cycle from what little we know about them, so it fits. They’re a weird mysterious magical type.

@Background Pony #16C6  
Cadence wasn’t a full-grown pony when she became an alicorn, so that size difference doesn’t really tell us much. She still had some maturing to do. But if from this point she eventually got taller than Shining Armor, I would have to concede that something like that was happening. Otherwise, nah.

@Millennial Dan
 
For another example, look at Cadance before. Her body type looks much closer to the average mare’s as she is a younger Alicorn
 

 
And then
 

 
Behold tall, lanky, big-horned Cadance. And then there’s Celestia who is super old and has those traits like whoah.
 
They’re a unique race of pony that we know works differently from others in some ways even if wee don’t know the details. It makes perfect sense that they would mature in their own pace with certain traits.
 
I also don’t see what you find so weird about it. In a show with so many weird things surely growing taller as time goes by isn’t that weird and out there for you?

@Background Pony #16C6  
That’s still just one size change, which makes perfect sense. I just don’t agree with the idea that they keep growing like some kind of lobsters.

@Millennial Dan
 
Again, the simple fact that they redesigned Twilight to specifically have a longer neck, longer horn and be taller rather than keeping her the same?
 

 
That took conscious intent. It didn’t happen by accident. And the fact that all other Alicorns happen to share those exact same traits specifically with the extent in age order?

@Poptard  
Hmmm…
 

 

 
Looks mostly like she got a longer neck. This was part of that weird redesign she got, which was never really explained. Makes it even stranger when you note how she looked in Twilight’s historical drug trip.

@Millennial Dan
 
Meanwhile, I’m looking at Season 1 vs. Modern Luna.

@Background Pony #16C6  
Who says they haven’t always been taller than average? We’ve seen several ponies like that.

@Millennial Dan
 
Reptiles? What the hay are you talking about?
 
I’m not saying they grow to the size of a house or anything, just that alicorns clearly get significantly taller and lankier than average ponies. It’s a design choice to differentiate them, and to visually show regal status.

@Background Pony #16C6  
Nah, I don’t think so. Like I said, they aren’t reptiles.

Flashlight senses tingling!
 
Woah. Flash looks kinda small in this one. That’s…actually rather adorable.
 
Hnnnng….

@Millennial Dan
 
Of course you wouldn’t see it every episode. Like I said, it takes building a new flash puppet and the show production won’t have the time. Plus, the episodes are supposed to take place in a short timeframe, not span various years so the diference wouldn’t be big enough. It would be nice, though, if as the new season and movie go by they made more changes to her design to reflect her growing into her role.
 
It’s a safe assumption that they made the Alicorns the way they did (lanky and big horned) so that their grace and imposing stature reflected their princesshood experience. Thats why Celestia is tallest, then Luna, then Cadance, then Twilight. As Twilight ages, it’s only seems fitting that she would look more like the others.

@Background Pony #16C6  
She had one size change. I haven’t noticed any further differences.

@Millennial Dan
 
The mere fact that the animators actually took the time to make a new flash puppet with her taller and with noticeably longer body, neck and horn once she became one, plus the fact that all Alicorns are taller and share those traits - and the extent lines up with their age - seems like a pretty clear indication. Why would I assume otherwise?
 
Plus, seeing her get taller just seems like a nice visual counterpart to character growth. As in, the height and grace of their bodies visually conveying their experience as Princesses.

@Background Pony #16C6  
She’s not that much bigger, and supposing that she’ll continue growing is merely conjecture.

@Millennial Dan
 
I meant as in the time of an older picture.
 
Twilight has already grown noticeably and she’s only been an alicorn for a couple months. She’ll be taller than a stallion once she starts growing into it I’d say. I’m sure Cadance and the other alicorns didn’t get to their current lanky tall forms in a day either.

@Background Pony #16C6  
So far, no, she still isn’t. As for having them being older, there isn’t any special reason to think she’ll be like a reptile and just keep getting bigger.

@Millennial Dan
 
This image is probably meant to be them a bit older. And Twilight is already taller then him as her Alicorn growth spurts keep kicking

@Poptard  
That’s what I was saying. Flash is a little bigger than Twilight is, so this image looks a bit strange.

@Millennial Dan
 
In the show, he’s actually slightly taller than Twi, thanks to the size upgrade stallions have received. For her credit, Twilight is also taller than the average mare, and maybe in a few years her Alicorn tallness will have kicked in.

What the… Flash is larger than Twilight. Looks weird.

…I don’t know why…But, there’s something…bitter sweet about this.

@Background Pony #6AC7  
i kinda changed my mind of ‘turning him into a god’ to ‘he’s a god from the start. flash sentry is the body he made to interact with ponies (he can transform to full god but chooses not to when things go bad just to see how ponies will do under pressure)