***
"Through that mirror a new, parallel world awaits. You'll soon know more about this place than even I do." Celestia beamed at the newly minted princess, pride filling her voice.
"I won't let you down, Celestia!" Twilight replied, determination set in her voice. Her admiration for Celestia filled her tone. She was an immobile rock in Twilight's psyche. A tender, compassionate, unblemished idol to be adored, but never approached. A loving friend she had cherished since her fillyhood, and a support she trusted with her very life time and time again.
With gusto, she charged through the mirror, heading after Sunset in hot pursuit. The world warped around her, and suddenly she found herself in an alternate Canterlot, a world very different from her own.
Twilight landed with a thud, and was surprised to hear a pair of "oofs" follow her own. She looked down to see Princess Celestia underneath her...with another version of herself in her embrace. Twilight blinked.
"I...uh...excuse me, well, me, did you happen to see a mare with a crown run pa--" She was cut off by her prized mentor's tongue, her coherent thought turning into muffled, indignant squawking. The other Twilight blushed, her tail rising at the sight.
"Why Twilight, when you mentioned that I would be getting a surprise present from you, I didn't imagine you'd be quite so...thoughtful." The parallel Twilight beamed at the praise, nuzzling against Celestia and leaving the original to watch in disturbed confusion.
"You...but...what? A-anyway, where did the crown go? I can't stay, I need to save Equestria!"
"You mean this?" Twilight casually floated the crown onto Twilight's head. "We found it after some orange pony bolted in a hurry and dropped her saddlebags. Something about needing to scrub her eyeballs for thirty moons or something." She shrugged. "In the meantime, I think 'Tia and I are going to hold a contest..." She trailed off saucily, her and the parallel version of Twilight's perfect, chaste and unblemished idol sharing a naughty look.
"To win the crown."
Twilight swallowed.