One day, in the comics section of the Equestria Daily newspaper, a strange diagram was published.
Nopony was certain where it had come from. An inquiry into the matter launched some time later at the newspaper's headquarters turned up nothing but hoof-pointing. The only clue was the initials "W.L." written in the corner of the comic, but Wild Legacy – assistant to the editor and the only pony with the appropriate initials and the necessary access to sneak the comic in unnoticed – flatly denied any involvement. Until new evidence could be found, the investigators were forced to put the case on hold.
The diagram in question showed a box with a circuit and a switch. The circuit was simple enough for a foal to assemble, and the required parts could be easily found at any local Tandy Corporation store. The power source was even easier: an apple. The switch required was called a "center off switch," one with three positions and which defaulted to the center (usually wired as "off" for any particular device). The diagram in the comics section of Equestria Daily had the switch helpfully labeled:
WEST – OFF – EAST
The triarchs of Equestria did not see as much of each other as they would have liked. The sisters Celestia and Luna kept opposite sleep cycles, catching only a few words at breakfast and dinner, and Twilight lived in a different castle entirely. Worse was the relationship the three had with Equestria's fourth princess, Cadence, who ruled over Equestria's remote northern territory rather than assisting in the rule of Equestria proper.
The problem, strangely, found its solution after the death of Shining Armor, sister to Twilight and husband to Cadence. The funeral was Twilight's first hint of what it meant to become an immortal alicorn, and she realized that she had five close friends who were all well past their primes. Her station as an immortal necessitated the cultivation of friendship with other immortals, lest she find herself alone. Twilight's plan eventually led to the first day of each month being clear of duties for all four princesses, allowing them to socialize in a setting that was not about being rulers of a nation, but about being friends.
Twilight had also left an open invitation for Discord to join them on the logic that one simply doesn't find another immortal being every day. However, her stipulation that he avoid using any chaos magic meant that he generally refused to partake.
So it was, several weeks after what had become known as "Trot Day," three regal alicorns and a particularly tired-looking Luna assembled at the Canterlot establishment "Pony Joe's Doughnut Shop" (although Joe himself had long since retired, leaving the business to his son John).
"Good morning, yer highnesses," welcomed the beige earth pony with an espresso machine cutie mark, "the usual today?"
"Please, thank you, John," Celestia nodded.
"Mhrmblgrl…" Luna added.
"I'll make that three orders of 'the usual' and one Death Wish coffee," John said as he scribbled down the order.
"Mblrrg!"
"Double shot of Death Wish it is, then, princess!" John finished writing down the royals' brunch order with a flourish and trotted back behind the counter to begin the preparations.
"You know," Twilight mused after the proprietor walked out of earshot, "that Death Wish blend contains more than 150% of the doctor-recommended daily maximum amount of caffeine. In a single serving."
Luna groaned, placing her head on the small circular table and covering her eyes with one arm. "I am a grown pony, and will do with my body what I wish. Besides, if three days of caffeine crammed into a single cup of coffee can kill me, we need to revisit what the word 'immortal' means." Luna groaned again, "Why are we doing this so late?"
"Because you got outvoted, auntie," Cadence replied as she wrote idly in a journal she had recently begun using to keep a record of her thoughts and activities. "You're the only one in the group who's nocturnal, and you have more than plenty of warning to shift your sleep cycle enough to enjoy a day with us. Now stop being such a baby."
Luna grudgingly sat up straight, but left her eyes covered. "Celly, can you install one of those clapper things on the sun?"
Celestia tittered, "I'll put that under consideration. However, your behavior begs the question: since you did know today was coming, why didn't you get your body ready for it?"
"It is those trot boxes; there are a lot of ponies having nightmares about them. I have seen everything from getting stuck in the wilderness, to Equestria getting abandoned, all the way to one pony last night who was having a dream about the apple in his box turning into some kind of alien monster and eating him."
"I guess I can kind of sympathize with the one about getting stuck," Twilight said, "but everything I've heard suggests that most ponies don't like going to those alternate worlds. I suspect it's a combination of the fact that they're each one big Wild Zone like the Everfree Forest – already unsettling for most ponies – and our herding nature. When you're out there, you're apparently not just far away from anypony else, you're completely alone." Twilight shivered a bit at the thought. "Anyway, abandoning Equestria seems rather unlikely."
"Well, the Crystal Empire seems to be safe from that fate," said Cadence, "as far as I've heard, none of my crystal ponies have been able to make a trot box that works."
A sneaking suspicion crept up on Celestia. "Girls, have any of you tried this whole 'trotting' thing? I must admit that I haven't…"
Cadence nodded, "I've tried a few times, when one of my ponies came to me for help asking why the box won't do anything. I'm reasonably certain it's something wrong with how they're constructing their boxes, though I'm not sure how. I've seen the design and it's pretty simple."
"Hold on," Twilight said. "You said you've only tried using the boxes that somepony else has made?" When Cadence nodded, Twilight continued, "I haven't done any testing on it personally, but from what I gather, you have to complete the circuit – that is, connecting the wires to the apple – yourself, and the box will only work for you. I've hypothesized that something in the circuitry becomes attuned to a pony at that point in the construction, locking it in to only work for its owner. That's just a hypothesis, though."
"What about you, Luna?" Celestia asked, only to find the midnight blue alicorn staring into the middle distance in the direction of the doughnut shop owner and the coffee machines. "Maybe we'll ask her once she's had some caffeine…"
"Anyway," Twilight said, "if none of us have built trot boxes and seen these other worlds, maybe we should try it? After all, we're free all day, we have plenty of time!"
Celestia nodded with enthusiasm, "That sounds like a wonderful idea! There's a Tandy Corporation store just down the street, too. We could get started right after brunch!"
As if on cue, the store's proprietor arrived with coffee, tea, and doughnuts, leaving the check on the table before returning to the other customers present. While Pony Joe's had no lack of business in part thanks to being known as a favorite of Equestria's princesses, it was often difficult to get customers to pay enough attention to order something while the princesses were actually present. While frustrating, John knew that he could more than make up for the stall in revenue as soon as the royalty had left.
Luna, for her part, had latched onto her mug of death-dealing coffee like a pony dying of dehydration might latch onto a bottle of water. The conversation shifted around her as the collected alicorns began to snack on their confections, and Luna even managed to join, once her mind was flooded with caffeine and she was restored to full wakefulness.
Less than two hours later, the party walked out of the gadgetry store named "Tandy Corporation" with bags full of enough components to craft four trot boxes, plus replacements in case some were damaged prior to their purchase, or more likely in case they were damaged during construction of the devices. The purchase included a full-page version of the original comic, making the details easier to see.
The group made their way to Cadence's guest quarters before unpacking their purchases, while Celestia sent a runner to the kitchens for a bag of apples: snacks and gadget components, all-in-one!
Cadence didn't pay much attention to the diagram, relying instead on her memory of the boxes whose construction she had inspected at home. Surely, there was something going on other than failing to build the device properly; there was no way each and every one of her subjects could fail in the same way, as all of the devices she had seen had been nearly identical.
Twilight laid all of the parts necessary on the floor, lined up and easy to identify. Piece by piece, she began to assemble her trot box inside the purple plastic container she had selected for herself. While intellectually she understood that there was no test involved, some part of her refused to let her attempt at building the trot box device in any fashion other than perfect.
On the floor next to Twilight, Celestia made an inadvertent example of why so many ponies considered her an image of perfection. Instead of placing each component into the device one by one as the two youngest princesses were, Celestia gripped every piece of the device in her telekinetic aura, assembling the entire thing in a single motion, with the exception of the apple on the chance that Twilight's hypothesis had a glimmer of truth to it. Celestia's final product looked identical to the original diagram, and she was finished long before the other three, so she grabbed a spare apple and began to nibble at it.
Luna did not begin her project at first. Instead, she studied the diagram, tracing the wires around the circuit with a hoof and moving her lips as though speaking to herself, although no sound came out. Eventually, she seemed to hit inspiration, and teleported away along with her allotment of gadget parts. Twilight and Cadence looked up in surprise, then looked to Celestia. Celestia shrugged, just as confused as the others.
Twilight and Cadence completed their respective boxes. Twilight's result appeared similar to Celestia's, her meticulous approach matching the diagram just as well as Celestia's direct copy. Cadence's box was a bit sloppier, with a rat's nest of wires concealed within her decidedly opaque box. Cadence's reliance on the memory of a job performed by multiple amateurs led to an aesthetically unpleasing result.
"So…" Twilight tried to fill the silence. "Do we wait for Luna, or do we go and look—"
Twilight was interrupted by the flash of Luna's teleportation. The night princess returned with two items in her magical grip: a dark blue peytral that could have been mistaken for the piece from her normal regalia save for apparently being hollowed with wiring visible inside, and a strip of brown flexible material Twilight couldn't identify.
"Silly Luna, you cannot forget the apple!" Luna chided herself. She grabbed an apple from the bag, inserting it into the peytral's wiring, and then began to work the brown strip into the backside of the barding, sealing it up.
"Luna, dear sister," Celestia sounded calm, but Twilight had experience differentiating what "calm" meant in Celestia's voice. This was the kind of calm that meant there was very potentially something wrong. "What is that material you're using?"
Luna had run into a snag, having accidentally worked a wrinkle into the join between the metal peytral and the thick material she was using to cover the backside. As such, her attention was divided as she spoke, "Oh, just some griffon leather I had left over."
If Twilight had been drinking, she would have managed a spectacular spit-take. Obviously, she was familiar with the concept of leather, but she had never seen any up-close like this. Celestia put on smile #32 ("I know you didn't realize what you're doing is wrong…") and said, "Luna, you realize that we are allies with the griffin aeries, aren't you?"
Luna nodded, finally managing to fix the error she had worked into the leather. "Of course."
"Do you see anything wrong with using griffon leather in the construction of something you intend to wear around your neck?" Celestia asked politely. Always politely.
Twilight gulped, "And I'm a little afraid to ask, but where did you find any griffon leather? It's not, uh… fresh, is it?"
Luna finished closing off the hidden compartment in her new peytral before responding, "It is not like Commander Grizelda is using it any more. I am certain her family, if her family line even still exists, appreciates that she continues to do good work." Luna smiled, slipping the new peytral around her neck. "As for where I found the leather, Twilight, it was in my forge, along with a number of other personal items. Celestia sealed the whole thing off and put it in a stasis spell after my banishment, so that it would be pristine upon my return. Have I not shown it to you?"
Twilight shook her head. "I wasn't aware you were a fan of metalwork, Luna!"
Luna beamed at Twilight's interest in her activities. "Indeed! Why at one time, I was the sole smith for the entire Equestrian army!" She paused, one hoof to her chin. "Granted, at the time both our army and country were much smaller, and Celestia and I were the only ones who really outlived equipment…"
Celestia, on the other hoof, looked a bit queasy. "If I had known you kept things like pieces of fallen enemy soldiers in your forge, I wouldn't have bothered with the stasis spell. Let the whole bunch rot into dust."
With a mischievous twinkle in her eye, Luna said, "I am certainly glad you didn't! Commander Grizelda is by far the most comfortable griffon I've ever worn!"
"So hey! How about testing out these trot boxes?" Cadence cut in, trying to change the subject. "And one trot peytral, I suppose. Um, where's the switch, auntie?"
"Right here!" Luna reached up to her cutie mark emblazoned on the front of her barding, and nudged it to her left. When Luna vanished without the tell-tale flash of a teleport, it became apparent that the image of her cutie mark was the switch.
"Well," said Celestia, "either her gadget works or I'm in the market for a new sister. What do you say, Twilight, are you up to the challenge?"
"What? But I—"
"I am teasing, Twilight. Any idea which direction Luna went?"
"Well," Cadence said, "auntie Luna did spend a great deal of time studying the diagram, so her wiring is probably the same as ours. Which means her left would have been the 'East' direction on the box, since her switch was facing away from her."
"Okay," Twilight said as she grabbed hold of her own box, "on three! One, two, thr—"
It's the small things one always forgets. Like, for example, how a number of the first users of the trot boxes returned with injuries consistent with falling. And how, for example, Twilight, Cadence, Luna, and Celestia were activating their own trot boxes for the first time from within the guest tower of Canterlot Castle. And that Canterlot Castle did not exist on the alternate version of Equestria they were trotting to.
At least the four of them all had wings.
"A thought occurs to me," said Twilight after she finished losing her brunch. "Well, two thoughts. The first is that we really need to find a way to tone down the effects of trotting."
Luna, who was flying stomach-twisting loops in the air over a hauntingly city-free version of Canterhorn Mountain, said, "Twilight Sparkle, I cannot imagine what in the world it is you are talking about!"
Giving the older princess a withering glare that went completely unnoticed, Twilight continued, "My other thought was about what Cadence said, how none of the crystal ponies have been able to make their trot boxes work. Cadence, your city rests on the ground, while the snow and ice are kept at bay by magic. If it weren't for that magic, how deep would you estimate you would be under the snow?"
Cadence was quick to answer, "The snow would be half again as deep as the Crystal Palace is tall… Oh," she said, as realization dawned upon her. "In this world, there's nothing to clear the space taken by the city. Anypony trotting would be buried alive in ice."
Celestia asked, "Are you suggesting, Twilight, that somehow these devices are protecting us from potentially fatal journeys into these alternate worlds?"
"Hmm," Twilight considered all the facts they had available. "I'm not sure that's quite correct; there were plenty of ponies hurt by trotting from second floor buildings or higher. If the four of us were unable to fly, we'd probably be dead right now. But maybe… argh! I need a blackboard!"
"I think," said Cadence, "Twilight is currently trying to figure out the science behind the trot boxes, and how they won't transport somepony into something solid."
"But that doesn't make any sense!" Twilight cried, managing to add her comments to the conversation despite drawing equations in the dirt with a stick and not paying attention to the conversation at all. "The air is still there! And we don't leave a vacuum behind when we leave…!"
Cadence watched Luna flying around above them while Twilight had a scientist's panic attack, and turned to Celestia. "Actually, now that we're here, I have a question for you. Can you… control the sun, here?"
Celestia looked up, staring directly at what nopony else could. "No," she said, "I can still feel my connection to my sun, even if it's a bit faint. But this is not my sun."
"I see…" Cadence sounded defeated. "So, how does it move?"
"Maybe it doesn't," Celestia said, her eyes never turning away from the blazing light. "Maybe it doesn't."