@Light Blade  
“I’M THIS MANY!”

Cady, how old are you XD

@Background Pony #5F05  
I hate when that happens. It’s almost as annoying as when the shift key gets stuck.

The A Button’s stuck.

“Does this bug you? Does this bug you? I’m not touching you! Does this bug you?”

@Background Pony #DE0E  
Well, actually, not only was Chrysalis likely paying little attention at the time (both because she was only putting the barest effort into imitating Cadance, and because she had no idea that the dance was important), but even simple dances like this are moderately complex.
 
Unless she’s some kind of dance savant, Chrysalis would likely need to see the dance several times (while actually paying attention) in order to memorize the motions long enough for her to get somewhere where she can safely practice it. Regimented dances aren’t trivial things you can flawlessly imitate after seeing them once or twice.
 
Honestly, the Sunshine Sunshine dance is actually pretty good security in this setting.

@Blissey1  
She was distracted because books exist somewhere.

@TexasUberAlles  
Hey, Twilight actually does stuff all the time!

@Poptard  
I mean, you don’t even really need investigation, Twilight straight-up demonstrated it to Chrysalis.

@Blissey1  
the whole point of them (from a story telling perspective) was to make it so the princesses couldn’t save the day themselves  
I think it was possibly meant to apply more to the thousands of Unicorns in the audience than the princesses, since their inaction is pretty easily explained in-universe by slow reaction time thanks to the relative scarcity of any of them ever having to actually do something themselves rather than let underlings handle it.
 
Also it still makes actual practical sense for the stated anti-cheating reasons.

@Blissey1  
Not really a good point at all, since it’s not clear it applied to the princesses.
 
Regardless, that’s what I said they did. We don’t know if they also dispel magic, which would be required to reveal a changeling.

@Fwelin  
I wouldn’t trust those things to find spies, all we saw them do was seal magic so it might just make a changeling be stuck as a pony which would make it even harder to tell if they were a spy.

@Fwelin  
I’m pretty sure that they do seal magic, since the whole point of them (from a story telling perspective) was to make it so the princesses couldn’t save the day themselves.

@Sparrow9612  
That’s assuming they dispel magic as well as seal it, though.

@Tragiclady
 
I know a guy.
 

@Poptard
 
There is a spell. Remember those doorways with the green energy from the Equestria Games episode?

@Poptard  
If only ponies could develop a better method of spy checking D:

“Fite me to prove you’re the real Twilight.”
 
To be honest, this is something a decent infiltrator would be able to pick up with only modest investigation. They should really develop a spell or something.

>edit  
>edited edit
 
screencap^editedit  
Need continue to “screencap^editedit^boop_edit

“…One more step and I will basically never stop punching you.”

“put em up! put em up!!”

Oh yeah, here’s the infinite lives cheat code…

@asdru  
Was a mistag for sunshine sunshine.

In heavy’s voice: “Fight me coward!”