Starlight often forgot she even had that time tracking spell running in the background. The spell wasn't her best work. Ideally it would categorize the time she spent, but unfortunately it mostly worked as a method to quickly review her day. She liked to watch her day at 100 times speed, quickly glancing through the day before writing in her journal for the night.
She slowed down her review of her day today though because so much had happened, meeting Sunset Shimmer, going to the human world, making new(?) friends. She couldn't imagine a better day.
However, there was a very, very odd anomaly when she had gone into the portal. Starlight had thought it had been a quick trip, but the time tracking spell had more memories than Starlight had experienced. She slowed down her viewing of her day, pinpointing the irregularity and watching it unfold.
Starlight Glimmer closed her eyes and followed Sunset Shimmer into the portal. She felt her entire body move into an entire separate realm of existence, stretching her and—
Plopping her down in the middle of nowhere.
Of all the places she had expected to see, it had not been an ethereal plane with an Alicorn Rarity standing in the middle of it.
“Hello Starlight, darling! It’s so nice to see you!”
Starlight stared at Rarity. She was wearing a gorgeous lilac dress that seemed to swirl like star dust all around her. It somehow matched the universe of stars and smoke around them perfectly. But it almost felt like the ethereal plane had been designed to match the dress and not the other way around.
“Uhh…” said Starlight Glimmer. “I take it this isn’t the human world?”
“No, not yet,” said Rarity, her amethyst mane twinkling and somehow ebbing and flowing like water. “But I know you’re anxious to get there, so let me get started!”
“Uhh…” said Starlight again. She knew she ought to have a million questions, but seeing Rarity as an Alicorn had thrown her so completely for a loop that her brain had not even begun processing what to ask. This was not helped any when suddenly her body began shifting and contorting in awkward ways.
“What’s happening to me!?” shouted Starlight.
“Sorry, this takes a bit of prodding, darling. Not to worry though, I’ll have you looking like a beautiful human version of yourself soon.”
Starlight couldn’t exactly feel what was happening to her. It was as if her entire body had been numbed. She knew something was happening to her hooves, torso and everything in between. Only Rarity’s mutterings every so often like: “No… that nose isn’t nearly cute enough,” made Starlight aware that anything was happening at all.
“And done!” said Rarity.
“Done?” said Starlight.
“With phase one, I mean,” said Rarity. "Now comes the best part, CLOTHES!”
“Clothes?” said Starlight.
“Well of course, interdimensional travelers deserve to look their best!”
Rarity brought out a dazzling array of outfits, shifting her eyes back and forth between the clothes and Starlight.
Starlight's brain finally caught up enough to ask a question: “How did you even get here?”
“Peer pressure,” said Rarity without skipping a beat.
“Wha—“ Starlight barely uttered before Rarity’s horn glowed and her entire body was encased in fabric.
“Okay, look. You started it,” said Rarity, still teleporting clothes onto Starlight. “There was this crazy thing that you made happen where time compressed all at once into a single moment and you became a Goddess of Time. And then Twilight became the Deity of Knowledge, and then Discord became a Deity of Harmony, and then Spike’s debacle where he became a Death Deity. Basically everypony was becoming omnipotent and I wasn’t about to abandon my friends—no matter how strange their new hobby of collecting godlike power was. Oh! That hat looks good—just need to figure out the outfit that will go with it.
“Well anyway, I caved to peer pressure and due to time compression shenanigans, I am—and have somehow always been—the Deity of Space,” said Rarity, who's horn flashed and Starlight felt herself wearing what must have been the tenth outfit in the last thirty seconds. “Really, there's not much for me to do besides monitor the constant expansion of the multiverse. Space will be rather boring until Rainbow Dash fails to completely protect the multiverse and commences the end of all things. Until then, I spend most of my time making outfits for interdimensional travelers to worlds that have a nudity taboo.”
“I— wha…?” said Starlight.
“Speaking of which, you’re going to need a nudity taboo spell for your human form,” Rarity's horn flashed. “There, that’s better.”
Starlight’s entire brain seemed to have evaporated and her only desire left was to stare. With a flash, she felt her body encased in yet another outfit.
Rarity squealed in sheer delight. “Perfect! You look magnificent darling, take a look!” Rarity held up a mirror.
Starlight took one glance and then started screaming.
“You’ll have to get over the shock of becoming human a few seconds from now,” said Rarity. “You’ll be forgetting this whole thing, anyway.”
“Forge—?“ was all Starlight managed to get out before Cosmic Rarity shoved her into a portal to the human world.