The obvious thing happens, and some other stuff, too.
One beautiful day Diamond Tiara and Silver Spoon were walking towards Sugarcube Corner to get a well-deserved snack after class. Diamond Tiara thought that it had been an exceptionally tough and pointless day for the two of them, what with none other than Princess Twilight Sparkle herself as the guest teacher and giving a lesson on the Magic of French Toast or something equally irrelevant to the two fillies. They already knew French Toast was tasty, after all. Anyway, she and her best friend were onto more worthy things now, so what did it even matter, she wondered. "So, Silver Spoon, what do you want to do after we eat?", she asked.
"Well, we could go see what the CMC are up to, I'm sure it'd be hilarious to watch them fail at whatever it is!", Silver Spoon replied with enthusiastic fervor. Diamond Tiara laughed while thinking about their preferred pastime and all the fun they'd had in the past with it, but then she thought of something better.
"I'd love to, and I'm sure those blank flanks would give us great material, but I was thinking we could do something else. How about we do something else, I found this book in the closet at home, and it looked really interesting. It's called 'The Key to Power' or something like that. Maybe there's something in there we can use to fulfill our obviously spectacular destinies!"
"Great idea!" Silver Spoon exclaimed. Later that night, after some delicious cake and some very boring homework, Diamond Tiara and Silver Spoon sat with the book before them on the floor. Turning the pages was difficult with just their hooves, but they managed, and they had to turn a lot of pages, as the first few chapters were disappointingly dry. However, eventually there came a page containing a spell that had a header reading, 'For the Greatest of Prestige and Glory, Follow these Steps.'
"Finally something worthwhile!" Diamond Tiara thought, but didn't say; as she had noticed that Silver Spoon drifted to sleep a while earlier. So, excitedly, she proceeded to sneak out of the house and follow the instructions herself; which included some hard to find materials she managed to borrow, so to speak, from that zebra living outside Ponyville, Zecoko, or whatever her name was, a circle with special markings (which she very much disliked drawing with her mouth and disgusting chalk, "Why can't chalk taste better?!"), and finally an incantation in a bizarrely archaic version of Ponish she struggled to comprehend. After assembling all the necessary things and performing the requisite preparations, Diamond Tiara proceeded to recite the incantation. And when she finished? Nothing happened. "Are you serious? I wasted my precious time, and still have to deal with that horrible chalk taste, and it was all for nothing?!" She mentally fumed. After that frustration, and multiple glasses of water to clear out her mouth and throat, she decided it was best she turn in for the night.
The next morning, Silver Spoon awoke in the guest room at Diamond Tiara's house, and realized that she and Diamond were alone and late for school. So, hurriedly, she sprinted down the hall to awake her friend. She knocked on Diamond Tiara's door, twice for politeness, and received no answer, so she went ahead and walked on in. And immediately froze in shock. "D-D-Diamond?? I think you should get up now . . . and maybe look in the mirror", she said.
At first, Diamond Tiara didn't hear her, but the second time she did, and she did as her friend asked, though she was annoyed at the rude awakening. "Oh my Celestia, I'm, I'm an Alicorn! The spell worked! Oh wow, Silver, do you know what this means?" She looked at Silver Spoon expectantly, and when she got no answer, she rolled her eyes and said, "It meansthat I can fulfill my destiny! And that you'll get to be right there beside me!"
Silver Spoon just stared at her, and then remembered why she woke Diamond Tiara up to begin with, "But, Diamond, we're late for school, we have to go." In response to which Diamond Tiara just laughed, and said, "School? School??? Silver, I'm a Princess now! School is now clearly beneath me, and you as my best friend. Come, we're going to pay a couple ponies in Canterlot a . . . visit."
That evening, in Canterlot Castle, Celestia and Luna were discussing their recent exploits and preparing to wish each other well, when suddenly a gray filly ran into the throne room. "Princess Celestia, Princess Luna, it's time that you step aside! There's a new, better Princess around, and her name is Diamond Tiara!" Silver Spoon screamed in delight.
As she said this, Diamond Tiara flew into the room, and alighted (With amazing grace for someone only having the power of flight for less than a day) before the Royal Sisters. "What's it going to be, she asked, are you two going to bow to your superiors, Silver and I, or must I force you?"
Luna just stood there in disbelief, and finally replied, "You can't be serious, you may have somehow gained a horn and wings, but you are just a fi-"; and then she was stone and spoke no more for all eternity. Celestia screamed in horror at her sister's fate and prepared to defend herself, but then, just like that, she was also stone and condemned to the same fate.
In the coming days, Princess Cadance would come along and be swiftly defeated and turned to stone, as well. And a few days after that Discord, along with Princess Twilight and her friends, the Necklaces of Candy or something like that, would come before Diamond Tiara and Silver Spoon, and ultimately they became wonderful statues themselves. Ones that really brightened the place up, mind you. Although, to be fair, the latter group did put up a fairly good fight before meeting their ultimate fate. "You know", Diamond Tiara, now the unquestioned ruler of Equestria, said to her best friend and right-hand, "I think we're going to love this life, you and I."
"I couldn't agree more!" said Silver Spoon, absolutely beaming. And they lived happily ever after, except for the CMC,
who were sentenced to on-demand heckling sessions for the rest of their lives at the whim of their Glorious Leaders for their heinous crimes.
