The Bucket of Sponges
Confound these ponies, why couldn't they just leave well enough alone? You thought to yourself as you stared at the gawking purple unicorn staring at the inside of your TARDIS. Honestly, she just had to follow you. Had to look inside a harmless bucket of sponges. Had to climb in to investigate just how you managed to fit inside. This was going to be a long day.
Now all she could do was gape as she tried to process just how such a large structure could fit inside something so tiny and insignificant. The purple one probably would start trying to analyze everything. She was always the smart one. Of course, nowhere near as smart as you, but then again, she was the one that actually managed to find this place. Gotta give credit where credit is due and all that rot. You really should have locked the door, but you had grown complacent in the fact that no one questioned you and your oddness.
Of course, you should have expected this. That unicorn was a stubborn one. Clinging to those adorable little scientific laws that others had come up with, you really had to fight down the urge to giggle every time she went on about how something you did was impossible. You couldn't though, that would blow your cover and then you would have to actually explain yourself. All you could do was bite your tongue and crack a joke.
"It's…it's bigger on the inside…" There we go; she had regained the power of speech.
You giggle, you really couldn't help it. That statement seemed to produce a sense of amusement and pride. "Of course it is, silly! How else did you expect me to fit inside?"
"You can't just stuff something the size of a house into a bucket of sponges!" There she goes, prattling on about what is or isn't impossible. You fight the urge to groan and facehoof at her stubbornness. How little she knew about reality. At first it was cute and adorable, now it was just starting to get old.
"Yes I can, and it isn't the size of a house, it's the size of Canterlot." You smile at her dumbfounded expression.
"It's dimensionally transcendental. To put it simply, the inside is in a completely separate dimension than the outside. The door acts as a gateway to it. Not really that difficult to do, actually."
Stunned silence. This is why you didn't tell anyone about these things. Always led to lots of questions. You really didn't know how your friend back home did it sometimes. Then again, he did love to show off…
She was giving you and all-too-familiar look. You knew that look. The look of utter confusion. It's only natural, you're not known for having the capacity to say, let along know the meaning of, such terminology.
She shook her head, obviously trying to shake off the confusion long enough to form a coherent thought. Didn't last long enough before she stumbled upon another question, "Ok, ok…I'll leave that for later. So…why does the outside look like a bucket of sponges?" Ah, that was inevitable.
"Oh that's easy. It's the chameleon circuit. It scans the outside and changes the exterior into something that would go unnoticed. Hence the bucket of sponges. After all, would you expect a bucket of sponges to be a doorway to a hyper-advanced ship?"
"Precisely. I'm trying to not be noticed."
"So…you're an alien…" Twilight again, looks like her mind is catching up to her. The shock must be wearing off. Oh well, the conclusion was inevitable.
You grin widely, "Yep, 100% wholly and truly extra-terrestrial!"
"Then why do you look like an earth pony?"
"Honestly? I haven't the faintest of ideas. Been like this ever since I came here. I think it might be the properties of this dimension, but I'm uncertain. I just gave up on figuring it out a couple centuries ago and just focused on blending in."
"Oh…wait, CENTURIES? How old are you!"
"532, give or take a couple of years. After a while, it all kinda blends together..."
More gawking. Always with the gawking. Really, the Princesses aren't the only long-lived ones out there. Geez.
"What the hay are you?"
You grin, "Time Lord."
"…That's not pretentious at all."
"Hey, I didn't come up with the name. Besides, it's kinda fitting considering what my kind are most well known for."
"And that is…?"
You fight the urge facehoof once more at her cluelessness. "Twilight, what did I say I was?" Honestly, just how did she end up as the Princess' personal student again? She really did have no common sense sometimes…
"You're…a time traveler…"
Now you're fighting the urge to pat her on the head as if she were a child. Though in all honesty, compared to your age, she may as well be a child.
"Yes, we are. This is a TARDIS, Time And Relative Dimension In Space, a ship capable of travelling though both space and time."
"That's amazing, if not slightly unbelievable, but then again…" Goodie, she was catching on.
"Yep, it most certainly is."
"…Why are you here?"
"Complete accident, really. Kinda fell into a crack and ended up here a few centuries ago. Couldn't go back, so I did the only thing I could. Set up a beacon and wait for someone to notice me. All I can do about it."
Silence fell once more. She wasn't looking at you, obviously this was a bit much, even for someone as smart as her. You felt awkward and a little guilty for hiding this from someone you considered a close friend.
"Twilight…please don't hate me for this…"
She sighed. "Look, I don't really know how to feel about this. It's not every day you discover that one of your best friends is a time-traveling alien from another dimension."
You let off a weak laugh. It really wasn't. Not even you wanted to try to calculate those odds.
"I suppose this does explain how you can do what you do."
You nod. Between the tech and your own natural abilities, you could easily be what everyone saw you as.
"What will you do now?"
That stops you for a moment. What were you going to do now that your secret was out?
"I don't know…kinda depends on what you do. I'd really just rather keep this a secret." You were looking down now. "I'm alone here. I'll outlive everyone short of the Princesses themselves. At some point I'm going to have to make an excuse to move away in order to prevent people from realizing that I'm not aging, then I'll be alone again."
Alone, that was something you didn't like at all. You tried your best to make friends wherever you settled down next and live there until your lack of aging became noticeable. Then you would have to move on; severing all contacts with those friends. That was never pleasant. Loneliness is a very unpleasant thing. At least the Princesses had each other…
"So let me get this straight, the reason why you act the way you do, go out of your way to be friends with everyone despite knowing that you will have to abandon them at some point in the future is because you're lonely?"
You nod meekly.
"So that's why you snapped when you thought we hated you?"
You nod. "Not one of my finest moments…"
She went silent for a moment, thinking. You sit down, not making eye contact. A hundred horrible scenarios work their way through your mind at once…
"Ok, I won't tell anyone."
"Cross my heart, hope to fly, stick a cupcake in my eye." She grinned.
You stared at her for a moment, before letting out a loud squeal of joy and glomping her. "THANKYOUTHANKYOUTHANKYOU!" Happy days! She wouldn't tell! Oh you just had to find a way to properly thank her for this. Wait, you knew the perfect way to thank her, a party! Not just any party though, THE party. The party to end all parties.
"Ooh, ooh! I know the perfect way to thank you for this!"
She laughed, "Don't tell me, a party?"
You backed off, heading to controls of your TARDIS, your signature grin on your face. "Not just any party, THE party, Twilight!"
She blinked, staring at you, "Umm…"
You grinned, "Don't worry, it's perfectly safe. We're off to the greatest party of all time! What's the worst that could happen?"
She stared at you for a moment, before letting out a laugh, shaking her head, "Pinkie Pie, you are so random."
You couldn't help but join her in her laughter as you worked the controls of your TARDIS, the sound of its engines joining your laughter as it whisks you both away.