@Kappe  
Cartoon physics… those poor trains; they’d keep needing to be repaired… I mean, the changeling COULD just refuse to leave the train and thus, be forced to stay on it until it goes to another station… which would be interesting to see them try to coax it out so the shield can propel them away.
 
“C’mon… we’ve got, um… love! And… cookies!”  
“No! I don’t believe you! Our queen has long since told us that cookies don’t exist!”  
“… Okay, we don’t have love, but, look, we’ll bake you some cookies…”  
“Liaaaaaarrrrrrrrrr…”

@DarkSpeed  
I stand corrected, it is probably a scanner. But what I said earlier still applies to the love blast shield.

@ShimmeringStallion  
Cartoon physics would dictate they would leave a bunch of changeling-shaped holes in the walls. But did you also know chitin is actually extraordinarily strong? You can only crush a bug because, well, its chitin is a tiny fraction of a millimeter thick and you’re 100,000 times larger. At their size, changelings would be incredibly durable.
 
I like to think the shield has some sort of provision preventing any of that from happening though. My favorite theory is that the shield would “assimilate” the intruder into itself, allowing them to pass through obstacles along with the shield, before popping them out a safe distance away. It is magic after all, and powered by love of all things.

@thps48  
I think that’s a scanner, but yeah, not a shield.

@cdcdrr  
I recall Luna actually making her own cap with the use of her magic.
 
Come to think of it, if there was a changeling on the train, that would’ve been excruciatingly painful… would it just be like a wall pushing them, as they’re crashing through the walls of the carts of the train?
 
Or would they be forcibly squashed like a bug and totally splattered all over the compartment?

@Kappe  
That’s not the shield, that’s the temporary hole.

@cdcdrr  
You’re right about Luna, but not the train.
 

@Kappe  
Actually, ponies could not pass through the shield, it was indiscriminate. The train and Luna had to pass through specific gaps in order to enter Canterlot.

@TheAbridgenator  
Fact: I mistakenly identified your avatar, and posted a response relating to who I had mistaken it for.
 
I don’t know my sci-fi… meh.

@KentuckyFriedScootaloo  
Not intentionally. Chrys drain him of the energy he needed to maintain the strength of the shield. He could probably keep a city-wide shield up for months. It is sort of his cutie mark. To protect, magic or otherwise. :3

@KentuckyFriedScootaloo  
No he didn’t. The changelings still had to bust through it as Shining was at the height of being mind controlled.
 
And yes, it could discriminate between ponies and changelings. The Mane 6 rode right through it on their train ride to Canterlot.

@cdcdrr  

 
That’s because Shining Armor was brainwashed at the time (so he set up the shield to allow changelings).

@Kappe  
yeah!

@ShimmeringStallion  
Oh, my dear Shimmering, it’s all true. Even the lies! No, ESPECIALLY the lies!

@TheAbridgenator  
It’s faaaaake…

@TheAbridgenator  
I think imprisoning Twilight was part of the plan because Chrysalis knew about the Elements of Harmony and how they work. Just like Discord, she wanted to remove the spokes from the wheel, and it wasn’t enough to discredit Twilight, she had to be broken. Trapping her in the same cave as Cadance, then taunting her incessantly to induce her rage made her ready to murder the real Cadance and it almost worked if it wasn’t for that secret handshake. If Twilight had killed Cadance, who knows what it would do to her when she finds Chrysalis wedded to her brother and realized she killed the wrong pony.
 
Even the three bridesmaid guards were meant as psychological attacks, since Twilight (and Cadance) could either refuse to hurt them and be subdued again, or fight them knowing she had hurt innocents. Any of these moves had a chance of damaging Twilight’s resolve and render her unable to fulfil her role as the Element of Magic. No Element of Magic means no Rainbow Waves. And if she didn’t let it get her down ever so slightly, you run the Catch 22 where her friends would have been appalled to hear what Twilight had done to escape and how cavalier she behaves to other ponies’ lives. Which damages their friendship, which renders the Elements useless, again.
 
And when all of that failed, all by a contrivance of Cadance convincing Twilight and distracting the bridesmaids with a plan so stupid, there had to be some kind of Want-It-Need-It spell involved to make it work, and navigating the caves without becoming lost, Chrysalis still trumps that by securing the tower where the Elements were kept before the Mane Six could arrive. Even though her plans within plans failed, Chrysalis still brute forced her way to victory.
 
The only reason she failed is that the workings of Shining Armour’s shield spell changed suddenly as the plot demanded, on which I call hax. It was last seen forming in place instead of expanding on from the caster’s point, and it didn’t originally discriminate between changeling or pony, so it should have either coalesced around the city, keeping the changelings inside with their prey, who’d now be unable to escape, or flung every pony out of Canterlot alongside the changelings, if it didn’t crush them against walls and ceilings altogether.
 
Chrysalis should have won outright because she laid out the perfect plan, but lazy writing denied her.

I recalled a pmv “if i were a pony”,  
In that story, chrysalis appears to be dead,super sad
 
 
and here,it’s good end

@Tetrominon  
Haven’t you ever heard of a thing called masochism? ;)

@TheAbridgenator  

 
No. You’re really not.

@mercurypony  
They probably can, I’d find it hard to believe a changeling would get nothing from the love of say a loyal dog, but the love an animal feels is probably significantly less than that of a human or pony.
 
I’ve always been more interested in knowing whether they literally need love as a necessary nutriment to survive, or they eat regular food and love just augments their power. Or a mix of both. That’s a question that’s always needed to be answered canonically.

I just realised but do changling HAVE to feed on ponies? Does there feeding work on animals to or it just weaker?

@Changeling38  
You really think nobody would notice Twilight vanished after an incident like she made? Her friends may have thought she was being a bitch but they didn’t disavow her; otherwise they would have stayed against her even after the big reveal. Unless she was swapped out for a fake Twilight…which would be a cool sidestory for S6, a whole Ben Reilly thing sans his stupid Clone Saga stuff.

@TheAbridgenator  
thanks man xD

@gittonsxv  
Grammar aside, that’s…actually fairly brilliant. A fuckton more thought than Vava put into his stuff. XD

@TheAbridgenator  
i am still with the theory that cadance never existed or is trapped in a hive somewhere.  
why would queen chrysalis put twilight under the castle with the real caddy and not a single guard apart from 3 stupid brain washed bride mares? because that caddy was also fake, twilight helps her “win” and get rid of all the changelings and when the wedding is over chrysalis now has no suspicion on her at all and she a very private kingdom way up north where few come knocking with a powerful unicorn stallion to sap the fuck out of.
 
i mean really, a species of creatures biologically designed for mind control and shape shifting does a raid on the capital in daylight instead of sabotage or anything like that? ye that sounds legit and not a massive red herring or a trick, bet you never noticed a few dozen ponies being replaced by changelings in the mess so when it is all over the “ponies” just return to there daily lives eh?
 
the whole chrysalis taking over shinings mind with the whole green eyes and him acting like a zombie was a red hearing, she did that so everybody would use that to look out for any changeling victims, little does the ponies know that the mind control is impossible to tell and is absolute.
 
adding to that theory is the crystal heart from the crystal kingdom, what does it do? it takes love and turns it into magic power…hmm love as a fuel source, never hear of that right?  
and then we have all the other bits, like a changeling just turning up one day in ponyville in that one episode but nobody freaks out, nobody mentions him, just turns up and leaves without a single alarm bell.
 
so that is my headcanon on all this.