Back at the old castle of the royal pony sisters there sat a little alicorn of blue. The once Nightmare Moon now was the youngest sister of Princess Celestia, Princess Luna. She sat there looking at a spot on the ground.
Just, well, laughing. The rest of the Element bearers were staring at her with 'What is she laughing at?' look. Well, almost all of them. Twilight Sparkle was rocking back and forth mumbling quietly to herself. No pony knew what was going on with Luna. They didn't notice Twilight in the corner, as they were busy trying to figure out what happened. Suddenly, there was a flash of light from the window just outside.
Then in came, the bringer of the sun herself, Princess Celestia. She started to proclaim her thanks, "I'm so proud of all of you for saving my..." she trailed off, looking at her surroundings; she saw her little sister, just laughing at, well nothing.
Then she saw her prize pupil in the corner rocking back and forth mumbling, she just made it out as, 'I'm a pretty princess and you all are my little ponies.' She then gazed back to the rest of the ponies that occupied the room, just as perplexed as she was. "Umm Luna? Do you remember me?" She asked as she slowly advanced towards her.
Luna stopped her laughing and glanced up. She has a frightened look on her face, staring at Celestia for a while. Then she suddenly screamed, "MOON MONSTER!”, then she got up as briskly as she could and dashed away.
She just scampered away like her life depended on it. Nowhere in particular though. She kept screeching the name over and over again. Soon she caught sight of the staircase that led to the exit. Then Celestia grabbed hold of her in her magic before she could stumble down the stone steps.
"Luna listen to me, you are okay. You're not in any danger of anything.” assured Celestia trying to stop her sister from being afraid of her delusions. "Luna, please be okay. I lost you once, I can't lose you again." She started crying.
Luna was struggling against her hold. She also seemed to be getting younger. She had a thought. If she put a sleeping spell on her, she could take Luna back to the castle in Canterlot. She started the spell, which many years before, she learned it from the one she was currently casting it on. It was successful; Luna slowly stopped her struggling, and was sleeping soundly.
While Twilight was still in the corner, she started yelling at something only she could see. Rainbow Dash having hearing her yelp soared over to her. "Girls! Over here!" Dash shouted but every pony was distracted by the princesses, until they registered that Rainbow had called them. "There is something wrong with her. She just keeps screaming her lungs out." By now all of them have joined her, the last being, and the princess. Twilight just continued her commotion, not paying mind to anything.
Then suddenly Twilight grabbed her horn and yelled, “GET IT OUT OF ME! IT’S EATING MY BRAIN!" She keeps trying to rip her horn off, but was stopped by Celestia when she grabbed her hooves from her horn. “LET ME GO! HE'S TRYING TO EAT MY BRAIN!"
"Oh my", said Fluttershy. She ran behind Applejack, who had her hat over her eyes. "W-what’s wrong with her?" She whimpered.
"I don't know. But it has to be the same thing that is wrong with my sister. She is having sound and sight hallucinations. It may also seem that they are regressing in age." Celestia replied.
She was looking at Twilight and Luna; she was still holding Twilights hooves in her aura and Luna on her back. They were getting littler by the minute. "If you look carefully you can see that they are getting smaller. As in, they are turning into foals. By my estimate, Luna is about the same age as a two year old foal of this time period and Twilight Sparkle is at three months."
The rest of the main six gasped but then Pinkie bounced up and down saying, "OHMYGOSHI'MGOINGTOMAKEA'YAYFORBEINGBABIESAGAIN'PARTY!" She was rambling, about what she would do at the party, and what kind of cake they would have, games and streamers.
Twilight was by now calmed down, well as calm as a baby can be. Celestia had let her grip on her go as she chatted with the five ponies in front of her. Twily just sat there in front of them looking at them all talking. She didn't know what was being said. Then she saw her new element that looked like a crown thingy. It was so shiny she just had to have it. So she crawled over to it while the big things were busy.
Rarity, having being confused by this whole thing inquired, "How did this even happen?"
"Yah ah don' get how this all happened. I need an explanation."
"As you all know, the initial blast from the elements was aimed at Nightmare Moon. It has turned her back into my sister from before she first became Nightmare. But also Twilight, she was the main source of power. This seemed to back-fire. From when me and my sister where young Discord tried to rip her horn off. Then in turn we blasted him into stone. We let him out eventually though. Back on topic, this seemed to have a memory sent to her through the blast. Now my sister is younger because she was sealed in the moon. Twilight is now younger because when Luna transformed back, this made Twilight regress as well.” explained Celestia.
"But umm will she remember anything from today?” asked Fluttershy.
"Only time will tell, in the mean time I will arrange for a room to be made in the castle for these two..." she looked on her back at Luna then down to where she thought Twilight was, but was shocked to find her missing. Her eyes shrunk a little as she called out for her student. "Twilight?"
She looked around the room in search of the little lavender filly. Twilight was chewing on her shiny crown. Finding her apprentice, she sauntered over. But only to back track a few paces as a horrid smell was received. "And some diapers..." The foal just looked up at her and beamed while holding her element in her mouth. Celestia smiled back as best she could. Given the stench was bad, and teleported them to the palace.
The main six just stood there for quite some time, they were confused by all this. They quietly conversed about their cool new necklaces for a few minutes. Then Pinkie uttered, "Well what are you ponies waiting for? Let's go get the party together!" She said happily bouncing away. She turned back to them, "Are you going to help me or not?" The rest looked at the pink pony and chanted in unison, "We're coming!" And they all left to plan the party.