Myself...
The moment had arrived. Twilight, Starlight, Spike, Sunburst and the others had reunited once again at the temple of Ponhenge. The Princess had Starswirl's journal, and her friends had gotten the items they needed for the summoning, each item belonging to one of the other Pillars of Equestria.
After each one of them left one item on each of the stone altars, Twilight and the two Unicorns shot their own beams of magic at Starswirl's journal. The magic sent another beam which connected the rest of the objects, and they provided a blinding glow as everyone awaited for the legendary ponies to appear...
But nopony came...
"Uuuuuh... Twilight? Was this supposed to happen?" Rainbow asked, feeling confused after the process.
"O-Of course not! Something must have failed!" Twilight answered, looking around frantically.
"But what? We already got the needed items for the summoning!" Sunburst replied.
"Well... Maybe something about the spell didn't exactly work as it should have worked?" Pinkie questioned.
"Sorry, Pinkie, but that actually wasn't any exact spell. We just had to imbue Starswirl's journal with some of our magic!" Twilight replied.
"I guess... it just failed, right?" Fluttershy said.
"It was worth the attempt, dear! We would not have known what could have happened!" Rarity replied.
"Well, that's right. At least we tried. Not anypony could say they almost got Starswirl the Bearded back along with his companions," Applejack explained, and the others nodded.
As Twilight looked worried, Starlight went to comfort her, "It's fine, Twilight. A lot of things could have happened, and this is one of them."
"A lot of things? Including the Pony of Shadows' return?" Pinkie asked, noticing then the looks from everyone else, "What?"
"Anyways, I think we should go back home," Twilight said.
Back at the Castle of Friendship, Twilight and Spike entered the library, the former looking around the different stacked books.
"Ok, Spike, I want you to reorganize the library while keeping in mind a few things: you'll have to get the diamonds book and put it beside the gold book, but not next to the Diamond Dogs book. You also need to get The Right Book, but just move it three places to the left. And finally, you may try to put the books related to dangerous things together, in alphabetical order. Any questions?" Twilight explained, leaving her assistant with a confused expression.
"Just one. Uuuuh... Could you tell me again?" Spike replied.
Twilight stared blankly at him, before answering, "Nevermind, I'll do it."
Right after that, she started levitating the mentioned books. For their surprise, she organized the books in just five seconds.
"Huh... I have never been that fast ever..." Twilight said, thinking about the situation.
Spike comforted the purple pony,"Forget about that, Twilight. Let's try to have a normal day without villains or other threats. What do you think?"
Twilight smiled, "Why not? I mean, what else could happen?"
And they went to make some royal chores inside the castle.
At night, Twilight was at her bedroom, getting ready to have a nice sleep. As she got comfy on her bed, she saw a curious thing. Looking closely, she realized what it was: her horn and hooves had grown a bit longer.
"Uuuuh... I know I'm an Alicorn now, but... I'm not exactly sure it works like this..." Twilight said as she inspected the rest of her body, not finding anything else, "Anyways... Tomorrow will be another day."
And then, she finally finished with everything before closing her eyes. Unbeknown to her, her body kept changing during the night.
Next morning, Twilight woke up feeling strange, so she went to the bathroom. After splashing her face with some water, she looked at the mirror...
...and there was Starswirl.
"GAAAH!!" Twilight yelled, her voice sounding completely different as she stepped back. The reflection on the mirror did the same, thus making her realize what was happening, "It can't be possible..."
"Twilight!? Is everything ok!?" Spike exclaimed from the other side of the door.
"Uuuh... Yes! Yes, everything is fine!" Twilight answered, despite knowing it wasn't true.
"Good to know it!" Spike walked a few steps away until something made him think, "Wait, what?"
Inside the Map Room, Spike was sitting on his chair as Twilight, now transformed into Starswirl and wearing his clothing, walked around trying to process everything. Starlight had also appeared, feeling the same surprise as the little dragon.
"I still can't believe you turned into Starswirl The Bearded! How did that happen?" Spike asked.
"I don't even know! I was perfectly fine last night, and this morning I woke up and I saw this!" Twilight said, pointing at her new body, "Ugh... Maybe some kind of magic infected me..."
"Ponhenge."
Twilight stopped walking as she and Spike turned to look at Starlight, "What do you mean?"
"Think about it: you and the others tried to summon the Pillars, but it failed. However, it may be possible that a little bit of magic from the temple, combined with the spell, attached some of Starswirl's traits to you, giving you his appearance and voice. It's a theory, but it may be what happened," Starlight explained.
Twilight thought about it, "Hmmm... I don't think there would be any other explanation," and then, she realized something, "This isn't going to be permanent, right!?"
"Not sure about that, but maybe we can find some way to undo everything and get you back to normal. Until then, you'll have to live as your idol," Starlight said, grinning as she said those last words.
"Uh... Fine. It's not like I got any other choice anyways," Twilight replied, still not accepting her transformation.
"Wait a minute! Does that mean I could also get my transformation?" Spike asked, a bit confused.
Starlight chuckled, "Spike, there are only six Pillars of Equestria and six Elements of Harmony. I don't think you would turn into-" her expression changed as she realized something, "Uh-oh..."
"What is it, Starlight?" Twilight asked.
"You turned into one of the Pillars. That same thing may also happen to the others," Starlight answered, making Twilight gasp.
"We have to look for them!"
"Maybe we can reunite back at Ponhenge!" Spike said.
"I'm gonna tell Sunburst about it! Come on!" Starlight added.
And the three of them ran outside, unaware that certain draconequus was enjoying the show.