In the magical land of Equestria lived three kinds of ponies: Earth, Pegasus (flyers) and Unicorns (magic) and there were four Alicorns (half Unicorn and half Pegasus) who were the Princesses.
Each pony has a 'cutie mark' (a symbol that represents that pony's talent) on their rear, or 'flank' as the ponies call their rears, but little ponies (or fillies) don't get their cutie mark until they are old enough to release the talent that makes them different from all the other ponies.
Princess Celestia went over what had been discussed at the meeting. She looked at a purple tree-shaped castle that sat in the center of the village called Ponyville. She used her horn to grab a quill and a piece of parchment and began to write:
'Dear Sunset Shimmer
Once again, I must politely ask you to return to Equestria.
This time, the whole world is in grave danger, and we need all the help we can get.
Please come quickly
Yours Sincerely,
Princess Celestia'
She trotted over to a fireplace and used her horn to throw the letter into the fire.
In an alternate world, a yellow-skinned girl with red and yellow hair wearing a blue top and black jacket with matching trousers and shoes, who was named Sunset Shimmer, was beside a horse statue, which was actually a portal between this place (Canterlot Hight School a big red school) and Equestria.
Suddenly a letter appeared out nowhere, and she read it, seeing it was for her. She looked at the school and the portal before stepping through the portal, but not before writing a note and sending it flying to her friends to tell them she wouldn't be here for a while.
Sunset Shimmer woke in pony form with a red and yellow sun cutie mark on her flank. The first pony she saw when she looked around was Celestia.
"Princess Celestia. I came as soon I got your letter," She said to the princess who used to mentor her before leaving her studies and starting the events of the film 'My Little Pony: Equestria Girls' (that's an actual film, I didn't make it up. Google it).
"Thank you. I wish I had better news for you, but it's an emergency. It seems that a terrible evil is going to threaten not only Equestria, Enchancia and Hawaii, but the entire world, including your new home," Princess Celestia said.
"What can we do?" Sunset asked.
"Go get Twilight and her friends, including Trixie, Discord and Starlight, while I gather my sister, Cadence, and Twilight's brother. You'd better get Spike too," Princess Celestia said, and Sunset ran off to do so.