He's here
In the palace gardens was a statue. A statue of some form of chimera, with its face trapped in a permanent look of fear and horror. Everyone in Equestria, however, knew that the statue was Discord, the embodiment of Chaos who, not a few hours prior, had swept Equestria into chaos and confusion. The statue seemed calm, but inside was an entirely different story.
Discord was angry. Very angry. He couldn't believe this had happened again. He would have been annoyed at his defeat, yes, but they just had to put him in this nightmare of a prison. It was pure hell being encased in stone. At least on the moon you could talk, walk and do something. Inside stone, you were trapped in one position, never moving, never seeing, never hearing. Complete and utter isolation until the end of days. He had never tried to do this to anyone. How could the so-called 'good guys' get away with this? He wasn't evil, unlike Nightmare Moon. He just wanted some fun.
That's when he felt it. A very small crack in his prison. Discord smirked to himself. It was obvious that, due to the breaking of the ponies friendship, the Elements of Harmony hadn't exactly been at full power. His prison wasn't completely escape-proof after all. Discord, summoning up the last traces of his magic, attacked the crack relentlessly, causing it to slowly grow in size.
Three days after Discord's defeat, the stone statue imprisoning him fell. Discord rose up from the rubble, chuckling quietly to himself. He had a plan. But first…
Discord turned his attention on the rubble. This would be fun. The rubble quickly flew together to form Discord. Discord burst out laughing at the result, quickly quietened himself, then flew off to Ponyville.
The next time she looked, Princess Celestia would be very surprised to see the statue of Discord facing her, blowing her a raspberry.
That night, Twilight Sparkle had invited all her friends to the Library. Which made Discord rather happy, as now he wouldn't have to go hunt down all six of them. He had a plan that should stop them from ever imprisoning him again.
The ponies (and Spike) were quite happy chatting. Happy, that was, until some kind of force pushed them into the walls. Wondering what was going on, they didn't have to wait long for the answer, as Discord teleported directly into the middle of the library.
"Discord!" Rainbow Dash shouted,
immediately trying to fly towards him, but to no avail. "Really? Discord?" Discord commented with the air of one who was merely talking about the weather, "I think we've known each other long enough for you to just call me 'Q'".
"Q?" Twilight Sparkle asked.
"It was a nickname given to me in my youth. I could never figure out what it meant…" Discord admitted.
"Um, Discord? If you don't mind me asking… What are you going to do with us?" Fluttershy questioned.
"Well, I'm going to give you a taste of your own medicine, so to speak. But first…" Discord walked over to Spike, "You're the dragon who can message dear old Celestia, correct? Here, send her this" Discord told him, holding forth a letter.
Spike complied, having immediately decided Celestia would be the one pony they would need about now. Indeed, she appeared within minutes of receiving the letter.
"Discord!" Celestia snarled, obviously angry at the Draconequus.
"Ah Celestia, how nice of you to join us." Discord commented, quickly hitting her with the same magic he used on the others.
"What do you want from us?" Applejack questioned.
"It's quite simple. I'm going to do something I've never done before, but you have done twice. Have a guess."
"Ooh! Is it a party!" Pinkie Pie questioned. After the Discord incident, she had been looking for any excuse to throw a party, in an effort to make up for her behavior, no matter how many times the other told her she was forgiven.
"No. Guess again." Discord said, with the air of one who could do this all day.
"You're going to seal us in stone until the end of time!" Celestia growled.
"The end of time? You were going to keep me in there until the end of time?" Discord asked, sounding a bit hurt, "You were close. You'll get to have a day in my prison. It might just re-evaluate your opinions. Oh, except you Spike. You didn't have any part in my prison, so you're free to go. And Luna is exempt, as I believe the moon was enough."
And with that, Spike disappeared in a flash of light. Another flash faded, to reveal seven stautes. Two Earth ponies, two Unicorns, two Pegasi and an Alicorn.
The first thing the seven noticed was the darkness. They couldn't see, feel or sense anyone. Each one of them was alone. Alone in the darkness.
The first thing Twilight saw upon awakening was the light. Had it only been a day? It had felt more like a year. The others quickly got to their feet, looking around for Discord. They didn't have to look far, as he quickly teleported into their sight.
"Well? How was the stay in prison Discord?" Discord asked.
"It was horrible!" Rarity exclaimed.
"It was s-s-scary" stammered Fluttershy.
"It was… so lonely…" Pinkie Pie mumbled, seeming close to reverting to Pinkimena.
"Yes, all of that and more. You were lucky. You only had to endure one day. I had to endure over 1000 years of that torment. Is it any wonder I wanted revenge?" Discord asked, annoyed.
Princess Celestia felt rotten. She knew a stone prison would be bad, yes, but she had no idea of the horror of it. "Discord…" Celestia sighed, "I apologize. I never knew exactly how bad your prison was. I promise to never make you go through that again."
Discord smirked. "Now for my actual plan."
"Your… actual plan?" question Twilight.
"Yes. You see, I was thinking… You could let me have small amount of chaos. Nothing huge, but constant streams of chaos across the land. Maybe chocolate rain for a bit, bigger apples later, but spread out, not all at once."
Celestia considered this. That would be infinitely better than re-imprisoning him or letting him run rampant. "I'll also throw ever one of those Galas you seem to hate so much into chaos."
.......
"Deal" Celestia agreed.
From that day forth, it wouldn't be unusual to have you house float into the sky for a few hours, or for it to rain chocolate milk, or for apples to mysteriously grow three sizes. It would also be normal, and quite hilarious, for many of these events to mysteriously occur, all at once, in Canterlot every Grand Galloping Gala.
And Discord? Let's just say he found a much better way of creating chaos.
Deep underground, in a small cave, three shadows moved. "Do you have the stuff?" one shadow questioned. Its voice was high and obviously female.
"Yeah, what about you?" said the second voice, which was deeper, yet still female.
"Yes, I have it." Replied the third voice. But this time male.
Lightning inexplicably crashed underground, revealed the shape of a certain pranking team composed of an Earth pony, a Pegasus and a Draconequus.