The planet of Chikyu is pretty odd, from an outsider perspective. There are anthromorphic sapients of every stripe and sort, the world president is a dog, its greatest warriors are alien monkeys, the average IQ (outside genius scientists or children) is somewhere below 50, and magic orbs raise the dead. How much difference would adding a pony that barely talks really make?
...quite a lot, apparently. Just ask Mr. Popo...if you dare.
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Dragon Ball Z Abridged crossover
Edit: Cover art by CaioCoia.
On DA: https://www.deviantart.com/caiocoia

Some people say that Celestia and Luna are useless. That they lounge in the castle while delegating all their responsibilities to hard working, underappreciated, exceptionally well-read students. That even when faced directly with threats to kingdom and country, they fold like cheap origami and wait to be rescued.

These people are correct. But there's a very good reason for it!

[Rated Teen due to a dark scene early on to set some backstory, and occasional comedic death]

To be inserted into Equestria, it's a dream come true for anybrony!

Meet the ponies!

Have super awesome magical adventures!

Use foreknowledge to avoid all those silly pratfall moments without screwing things up and causing irreparable harm to the Mane 6...uh...hopefully!

And all for the low cost of possessing Princess Luna, denying her any real freedom or the ability to move on with her life since she's in your head and you're walking around as Nightmare Moon!

Yeah...there had to be a catch in there somewhere, didn't there?

It's been a long, long time since Spike was stolen from her, but Twilight hasn't forgotten nor forgiven. After a long and arduous journey, she has finally found him and his kidnapper.

She will save him.

No matter the cost.

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Featured on EQD.
Now with Dramatic Reading by Joehighlord!
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Side story: A Dragon Whispers Her Name

Set in the future, after an unspecified amount of time has passed. Accurate to the canon set before 31/01/2013.
Inspired and loosely based on the short film 'Sintel'.
Elements of the story taken from the 'Where the World Ends' universe (by hlissner).

Image is fanart by NCMares.
Pre-read by ThoseRemainingSilent and Bleeding Rain.
Story formerly known as 'Twintel'.

Twilight Sparkle has disappeared. Not just from the face of Equestria but possibly from the face of her universe itself. She must now learn how to survive in a place unlike anything which she has experienced thus far. Luckily she has a friend out in the Wasteland. Join Twilight and The Lone Wanderer as they try and discover a way to send Twilight back to Equestria. Of course this is the Wasteland and things are never as simple as they appear...

Now has a Tumblr

Celestia decides to see just how right she was in her choice regarding Twilight's ascension. But upon stepping off the Cutie Map, the world is shattered and she aims to find out why.

If you're interested in more, Apathy is the sequel.

After a tragic accident, a human ends up in Lord Tirek's body, as part of an attempt to reform the villain after his recent escapades. While the hero of our tale is trying to make sense of his new surroundings, the rest of Equestria thinks that the most terrible threat that their world has ever seen is back...
And the powers that be are definitely not happy about it.
New Cover Art By Shadow Bolt

The nation of Equestria has been exploring their little slice of the universe for some time now. From launching probes into deep space, to landing ponies on the moon. Sending things beyond the grasp of their planet has become almost routine. However, with every mission into space, there comes a time when the voyage must end. What happens when Equestria experiences the end of a voyage that they didn't begin?

Updated and Revised on October 5th, 2014

Celestia has never used her full power.

Ever.

But that might be about to change. Chrysalis has contacted her and requested a meeting out in the middle of nowhere. Celestia expects a trap. In fact, she's hoping for it.

Featured: Because you guys are way too nice to me. Thank you all!

Now with a Spanish translation: https://www.deviantart.com/spaniard-kiwi/art/Un-mundo-de-fosforos-923171362

Twilight gets a visit from a familiar stranger. Except it's not a stranger. It's Twilight, from the future. As future Twilight hangs out with past Twilight, past Twilight comes to a startling realisation... Her future self is kind of a jerk!

Quite obviously blatantly copied from based and expanded from this comic by 1trickpone.

Preread by Chicago Ted, thanks!