Each of the three tribes, the Pegasi, the unicorns, and the Earth ponies, cared not for what befell the other tribes, but only for their own welfare. In those troubled times, as now, the Pegasi were the stewards of the weather, but they demanded something in return: food that could only be grown by the Earth Ponies. The unicorns demanded the same, in return for magically bringing forth day and night. And so, mistrust between the tribes festered, until one fateful day, it came to a boil. And what prompted the Ponies to clash? it was a mysterious blizzard that overtook the land, and toppled the tribes' precarious blizzard led to famine, at which the three tribal leaders eventually agreed to meet for a summit and decide what to do about the snow, but this only devolved into arguing and blaming each other. The leaders of each tribe then decided to journey to a new land. They all arrived at the same place, and soon began fighting over it, and the blizzard quickly followed and so the paradise that the ponies had found was soon lost, buried beneath a thick blanket of snow, and hard feelings. The leaders' assistants find out windigos are causing the storm by feeding off of hate. The assistants' friendship creates the magical Fire of Friendship which does away with the windigos and the snowstorm. The three leaders then decide to join forces and found a country shared by all three tribes, and name it Equestria. Then, there were two regal sisters who ruled together and created harmony for all the land. The eldest used her unicorn powers to raise the sun at dawn. The younger brought out the moon to begin the night. Their subjects, the ponies, played in the day but "shunned" the night and slept through it, which made the younger unicorn grow bitter, eventually refusing to lower the moon to make way for the dawn. Her bitterness transformed her into a "wicked mare of darkness", Nightmare Moon. The elder sister reluctantly harnessed the power of the Elements of Harmony and banished her "in" the moon, taking responsibility for both sun and moon, maintaining harmony in Equestria.
*Note: This is based off of The Hub's My Little Pony: Friendship is Magic. It is an animated series based on Hasbro's popular My Little Pony franchise. The show premiered on October 10, 2010 on Hasbro's The Hub channel, and has continued on to its third season. This incarnation of the franchise is referred to as the fourth generation, or G4, of My Little Pony. The show was developed for television by Lauren Faust, who is known for her work on two of Cartoon Network's popular and critically-acclaimed franchises, The Powerpuff Girls and Foster's Home for Imaginary series stars a unicorn pony named Twilight Sparkle, a student of Princess Celestia, the ruler of the magical land of Equestria. The princess gives Twilight the task of learning about friendship and sends her and her assistant, a young dragon named Spike, to Ponyville. There, they meet some interesting ponies, including action loving Rainbow Dash, glamorous Rarity, hard-working Applejack, timid Fluttershy, and hyperactive Pinkie Pie. Together, they go on adventures, solve various problems, and learn about the magic of friendship. The series has garnered a cult following, whose members are often called bronies.
Citation: wiki/My_Little_Pony_Friendship_is_Magic and wiki/Equestria