This is how A tale of two regal sisters goes in Elements of Harmony, Part 1.
[The story begins with a book as it opens by itself to a page with the words "Once Upon A Time..." written across it as we zoom on it]
Narrator: Once upon a time, in the magical land of Equestria, there were two regal sisters who ruled together and created harmony for all the land. To do this, the youngest used her unicorn powers to raise the moon at dusk. And the elder brought the sun to begin the day. Thus, these two sisters maintained balance for their kingdom and their subjects, all the different types of ponies and Transformers. But as time went on, the elder sister became resentful. The ponies and Transformers rested and slept in the night, but played and worked through the day. One fateful night, the elder Alicorn refused to lower the sun to make way for the dusk. The younger sister tried to reason with her, but the bitterness in the elder one's heart had transformed her into an evil sun godess: Vulcanna Daybreaker. She vowed that she would shroud the land in eternal day. Reluctantly, the younger sister harnessed the most powerful magic known to ponydom: the Elements of Harmony. Using the magic of the Elements of Harmony, she defeated her older sister and banished her permanently in the sun. The younger sister took on responsibility for raising both sun and moon.
[Cut to Optimus Prime reading the book]
Optimus Prime: And harmony has been maintained on both Cybertron and Equestria for generations since. Hmm. Elements of Harmony. I think I've heard of those somewhere before. But where?
[Later Optimus is heading to Iacon when he runs into Jazz, Blurr, and Windblade]
Jazz: There you are, Prime.
Blurr: We were looking for you.
Windblade: Ironhide's having a little get-together at the gladiator field. Wanna tag along?
Optimus Prime: I'd love to, Windblade. But I'll pass. I have a lot of studying to catch up on.
[He transforms and drives away]
Jazz: [sigh] Does that bot do anything except study? I think he's more interested in books than friends.
[Optimus drives on]
Optimus Prime: I know I've heard of the Elements of Harmony.
[He reaches Iacon and arrives in the Hall of Records where he finds the other Autobots]
Bulkhead: Hey, Optimus.
Arcee: Where've you been?
Bumblebee: [beeps] (translation: What took ya?)
Ratchet: Have you found a new quest?
Smokescreen: We've been waiting for ya.
Optimus Prime: Autobots, have any of you heard of relics known as the Elements of Harmony?
Bumblebee: [beeps] (translation: Um...)
Ratchet: Not really.
Smokescreen: How would I know?
Optimus Prime: [searches through books on shelves] No. No. No. No. No. No. [groans in frustration] Ratchet!
Ratchet: Ah-ha! Predictions and Prophecies. [to Optimus] It's over here.
[Optimus goes over to Ratchet and he gives it to him]
Optimus Prime: Ah. [flipping the pages] Elements. Elements. E. E. E. Ah-ha! [reading] Elements of Harmony. See Mare In The Sun? [thinks] Mare. Mare. [flips the pages] Ah-ha! [reading] Mare in The Sun. An old legend. A powerful pony who wanted to rule the land and shroud it eternal day but was defeated by Princess Luna. But legend has it that on the longest night of the thousandth year, the sun's peak at mid-day will aid in her escape and she will