A great flash of white exploded over the whole town of Ponyville before Twilight and her friends were able to see what had happened. When they were able to visualize the town, everything was as destroyed and the mess was yet to be cleaned up... But there was one important thing missing.
"Where's... Where's Giganto-Pinkie?" Rainbow Dash asked with confusion.
As the white haze started to clear up, the ponies finally saw Princess Celestia and an unconscious (and regularly sized) Pinkie Pie was waiting in the middle of town.
"Princess Celestia! The princess did it!" Twilight screamed. All the ponies cheered and gathered around the Princess and the sleeping Pinkie Pie, and the Princess quietly hushed them. The crowd's noise slowly abated, and Twilight was the first to speak.
"Princess Celestia! I'm so sorry for what I did! I thought it would be healthy for Pinkie to start a diet, and then she started going all crazy, and then-"
"Please Twilight, there is no need to explain. If anypony needs to explain things, I should be the one."
"What?" The five main ponies and dragon said in unison.
"As of now, I put Pinkie Pie back to regular size, boosted Pinkie Pie's metabolism up fifty percent, and made her unconscious. Now, I should have explained this beforehand, because I knew that one day, this would happened." The white shining alicorn sighed. "Twilight, tell me this. Can a pony live without air?"
Twilight looked at her in confusion. "Well, of course not. It's a simple fact. Ponies need air to live."
"Exactly. For Pinkie Pie, She has had so much candy and fat-inducing foods for everyday of her life that it seems like a simple regulation for her to need than something she can just choose to want. So if you take away air from a pony, a pony would do whatever he or she can do to get air back. That was what Pinkie Pie had been doing."
"What a minute!" Twilight interrupted. "I had sent you three letters about my friends and I planning a diet for Pinkie Pie beforehand! Why hadn't you said or warmed me about anything?"
"Well, I was very busy while handling very important matters." Princess Celestia grinned sheepishly.
"Wait ah minute!" Applejack also interrupted. "This here problem has gotten on the news! Ponies sent letters to yah once it happened! Ah even watched Twilight send one, with that urgent stamp, too! What took yah so long?"
Ponies started arguing all at once toward the Princess, and she stopped them before they had to time to argue more.
"Okay, my little ponies. I know I had been a tad bit late on this situation. But at least everypony knows what would happen if you even mention diets by Pinkie Pie, and now it won't ever happen again. Also, I need everypony in Ponyville to make haste of knowing this one thing. So everypony, please, listen up... Vinyl Scratch? Are you still here?"
The white DJ mare got through the crowd. "Uh, here, your highness."
"Do you still have one of your speakers nearby? May I use one of them?"
"Uh, sure, give me a second."
After five minutes, Vinyl Scratch had set up one of her huge black speakers for Princess Celestia to use.
"Now, everypony, this is very important. Once we get this town cleaned up and back to how it used to be, we must never speak of this to Pinkie ever again."
The crowd bursted with questions, most of them being "why".
"I erased Pinkie's whole memory of this dieting situation ever happening. If she is to ever remember this ever happening, she will think herself as a monster. Not only will this stab at her self-confidence, but this will cause her to remember the memories of the diet, and start on her candy rampage once again. So, we will have to organize this together to make sure this is forgotten!"
From that moment on, Ponyville cleaned up all the broken houses and buildings, and Pinkie Pie woke up thinking that an earthquake simply happened, and that she had slept through it.
Due to Princess Celestia boosting her metabolism, Pinkie Pie never got fat from her eating habits anymore, and she continued happily through life eating as much junk food and candy as she wanted.
As for the rest of Ponyville, the whole problem with Pinkie Pie was forever known as the "Wreckage of Year 12", and to the pink party mare, she thinks that they're just talking about the earthquake she never saw.
Laws passed through Ponyville, and the mayor approved the tenth city law to be, "No ponyfolk of Ponyville shall ever demand 'her' or descendants of 'her' any such diets, or solutions that imply diets." Pinkie Pie thinks that the law is about Princess Celestia, and any other way, she barely cares about it or what it's talking about. Pinkie Pie barely listens to laws. Mostly of those referring to physics. But any laws, nonetheless.
Pinkie Pie happily lives her life never knowing about what happened those couple days. But many prophecies theorize that one day, somepony will slip up and accidentally tell her, and the pink monstrosity will come back again.
For now, Ponyville can't risk that. They keep the secret well hidden from pink mare, and laws were later made to stop any ponies from talking about the Wreckage of Year 12 in public.
Before Princess Celestia Went To Ponyville
"Are you ready, sister?" Princess Luna said to her big sister, clutching her hooves to the side of the slide.
"I'll race you to the bottom... Readysetgo!" Princess Celestia launched herself through the white tube and all the way down the slide.
The two princesses were supposedly doing work, but for now, the work they were doing was sliding down the giant temporary tube slides that proceeded in the throne room.
"Weeeeeee!" They both said in unison. The slides were so long and complicated that it had been ten seconds and they weren't even halfway done.
One of Celestia's guards walked in. "Princess, there is a pile of letters here for you. Many of them are urgent."
"Not right now, Stalwart! I'm having the time of my life!"
"Uh... I know this isn't any of my business mam, but this seems REALLY important... They all have urgent stamps and are from Ponyville. It is also on the Ponyville news that a giant pink monster pony is destroying the town..."
"That can wait! Weeeeee!" The Princesses finally got to the bottom of the slide.
"Uh, are you completely sure, Princess? The whole town of Ponyville is in panic mode as we spea-"
"Let's go again, sister!" Princess Luna flew all the way up to the beginning of the slide, and Princess Celestia followed, giggling.
"Okay then..." The guard scoffed and threw the letters on the floor. "Do you mind if I join too?"
The two princesses looked at each other and shrugged. "Get up here, Stalwart!"
"Yay!"