If pinkie pie is a changeling spy or the animator has made an error on their part.

4914702

>wings

Surprise!

LOL another alicorn error, ya think they would have caught that by now.

Well there WAS that filly who shapeshifted during the assault...

Oh no! Larson's at it again!

4914702 I call changeling spy! They simply pretended that gunk reveals who they are so the resistance doesn't invent any new tests to ferrite them out and can infiltrate at their leisure. I mean, that's what I would do and Chrysalis may be a bit of a inattentive megalomaniac but she's not a idiot.

4915467
Or perhaps it doesn't really reveal changelings, but alignment (friend, neutral or foe).