I told you to go right

Turns out I wasn't the only pony to have the problem of an incredibly low outer temperature but feel fine. A large group of ponies were sat in the Doctor's waiting room, all alongside their lovers who looked terrified that their own mare/coltfriend might be cold as stone due to unknown forces. I took a seat next to a stallion wearing a gold chestplate, whose lover was wearing gloves and a scarf as she leaned on him and shivered.
"You too, huh?" I asked him.
"Yep." he replied. "Freezing outer body but feel fine?" I nodded.
"Yep, you've got the same as me." I chuckled. "Though I must say, this only seems to have happened to couples? Bit suspicious, especially with the Changelings hiding in Canterlot..." Suddenly, the mare leaning on the stallion's pupils shrank slightly, and began darting around.
Gotcha, bitch.
"I suppose so," he replied with a nod, gesturing to the waiting room. "I mean, look around? There isn't any SINGLE ponies here, I don't think. It's only couples I'm seeing. And, to be honest, some of the ponies that are with their lovers look nervous now. Even you."
"Woah, woah!" I laughed. "Bit of an accusation, mate! Let's not go blasting everypony's faces off just yet, we haven't Spy-checked 'em."
"What-checked?"
"Ah, it's an in-joke, between my friends and I."
"Yes," Luna giggled, "And me!" Oh, shit. Is she a Changeling?
"Really? I don't remember telling you, Lulu." I narrowed my eyes, and so did the guy next to me. "Let's test your knowledge, then. What will Painis Cupcake do?"
"What?" she asked in reply.
"What will Painis Cupcake do? Come on, normally you'd be rifling through the filing cabinets in my head to find out."
"Of course, that's what...uh, I'm doing..." After a second of silence, she spoke again. "He will heat you?"
"Wrong." I smirked. "Next question: is it good to kill a Spycrab?"
"Yes, definitely."
"NOPE. Final question: How did we meet?"
"Oh! That's easy: we had a nice meal together, and I cast a love spell on yo-?" Immediately, I braced myself in case I was wrong, and made a decision that might have ended up affecting my marefriend's foal-bearing ability. I slammed my hoof into her gut, causing her to let out an un-pony-like screech. The whole waiting room turned in shock, some ponies more shocked than others. Recovering, 'Luna' glared at me with eyes glowing a slight green.
"What the BUCK, Thunder?!" she cried with a fake sadness. I grinned.
"Y'all're 'bout t' have a real baaad day." I chuckled, punching my hoof into my other as I stood up. Once again, to the sheer horror of everypony in the room, I cracked my right forehoof into 'Luna's' jaw. A trail of green spewed out, which was the only signal I needed that I could really let loose with this next volley. My hooves were fast as lightning, 'cause I was kung-fu fighting as I repeatedly hammered her face with punches. Finally, after around the 23rd blow, she fired a GREEN bolt of magic at me and sent me flying across the room. When I looked back, the image of my marefriend was now replaced by a battered Changeling, mouth drooling angrily onto the floor.
"Enough, foal!" it laughed, a slight Scottish accent reminding me of Sheogorath from Skyrim. "I've already hidden your Princess, and fed from your love. But well done, on your part, because you stopped me before the headaches began. So no mind control for me, yet. Well, maybe a little." On the last syllable, my hoof moved of its own accord, before socking me in the jaw repeatedly.
In reply to this feeble attempt at injuring me, I lunged at the creature with a minor wing thrust, which barely did anything due to my wing, and threw it to the ground. After a few good right hooks, it was stunned enough that a notification appeared telling me 'FINISH HER!'. Her? I can't hit a-ahhh, sod it. Hope you spent a while strengthening yourself in case you got beaten to death with your own jaw, bitch.

And, to save me from having to put a warning for 'gore in chapter 79' in the description, let's just say that funeral ain't gonna be open casket.

Anyway, when I was done Spy-checking in an über gory manner, I stood up. Turning around, I saw that apparently the other ponies that went cold on the outside were in the later stages of being fed on. Their eyes were now derpy, and they just stared ahead. Meanwhile, the Changelings around began to undisguise and start smiling wickedly at me because apparently I looked tasty.
"Sup, fellas?" I smirked at them, still holding the thigh-bone of their comrade and stained green with [CAN'T SAY IT BECAUSE OF NO 'GORE' TAG LOL]. Oh, and some blood coating my legs, too. "So, where you sending me, lads?"
"Down below." replied one Changeling, as the whole room went green and there was a ring of fire surrounding my hooves. I gestured to the ring, smirking.

"That's pretty cool." I chuckled, before pretending to press a button. "Lift going down. Beeeeep."

"Ugh, fucking Changeling bastards..." I muttered, sitting up in the darkest place I'd been in for a while. I recognised the floor as stone and crystals, but I couldn't see the walls. There was no light, either, except a few slivers coming from cracks in the surface, so I'd have a lot of trouble finding my way out. "The hell am I...?" I muttered. Suddenly, there was a flash of light as the crystals around me illuminated with 'Cadence's' face.
"The caves beneath Canterlot." she replied, smirking. "It's where all the ponies go that try to lead my plan astray."
"Well it's a shitty plan!" I shouted back. "And you realise that I've been here before, right? Despite it being a long time ago, I can probably remember my way out!" She just laughed.
"Really?" she giggled in a grating voice, before seriousing up. "Oh, and just in case you DO get out and start telling everypony, I have to cast a minor amnesia spell on you so you forget it was me. Sorry, nothing personal, it's just my plan to take over a country." The image faded, and so did my conciousness.