Several years have past since the happening of the sonic rainboom, and the little filly had grown up to be a beautiful young mare. This mare had just been given her first job at the local weather team in the small village of Ponyville. She was just going to get a look around town when it appeared.
“WELCOME TO PONYVILLE!”
The young pegasus mare didn’t even have time to understand what was happening, as she was tackled to the ground by what felt like a bullet, but in reality was an overly excited mare.
Looking up, she was met by a pink mare with intense blue eyes sticking her muzzle in her face. The pink mares breath had a faint smell of cupcakes and frosting, and somehow, the pegasus mare thought of all laughter she evrr heard,all at once...
“What the flying feather do you think you're doing? Get off of me!” the mare on the ground screamed, trying to get out of the other mares grip.
Noticing the other mares struggling to free herself, the pink mare moved away from her, smiling sheepishly.
“Oopsie. Sorry for that. I’m your new best friend Pinkie pie!” the mare exclaimed, smiling.
“Wait, you just decided we’re best friends? But I just met you...and frankly, I don’t normally hang out with ponies who tackle other ponies and make them their best friends without even asking!”
Upon hearing this, Pinkie Pie, deflated like a helium balloon being punctured. Her pink mane, which had been the curliest mane the other mare had ever seen, became the straightest mane she had ever seen, and the hole color palette of the pink mare seemed to become dull and uninteresting.
The young pegasus mare could immediately, despite not realizing why, feel that something was horribly wrong. It was like not only the pink mare, but everything and everypony seemed to have become gloomier as well.
“I get it...all I wanted was to make you happy, but maybe you don't care about your own nor others happiness...and now I’ll have to cancel your ‘Welcome to Ponyville’ party!” the pink mare whispered sadly, turning her back to the pegasus mare and starting to walk away.
As the pegasus mare watched the pink mare walked away, the desperate feeling that everything was wrong, oh so wrong, was unbearable for the young mare.
“Wait! I-I’m sorry...I will come to the party...it sounds fun.” The mare exclaimed, just to make the feeling go away. The feeling of that she had somehow let down destiny itself.
The pink mare looked up, and the other mare watched as she bounced high into air, her mane going back to being a big curly mess and her features lightning up, the light from her spreading to everything and everypony around her until the whole world around them appeared brighter than before.
“YAY! LET’S GO NOW!” the mare exclaimed, running off into the distance, while the other mare did her best to follow her.
Finally, the pegasus mare ended up inside a big bakery, which operated inside a house designed to look like a gingerbread house with a cupcake-shaped tower on top.
Inside, one of the biggest parties the mare had ever seen was going on, and it was all dedicated to her.
Seeing the Pinkie Pie laugh and dance with ponies the pegasus mare had never seen before, she remembered. She realized why seeing the mare sad had caused her such pain…
Because she had created the eternal happiness this mare possesed to begin with. It was her rainbow explosion, the stunt that made her so famous, that had created this mare as she saw her: Happy, innocent and somehow made of laughter.
She knew what her mission was, and would be. She was going to protect this mare, protect her happiness. Forever.