This probably has already been done, but... I haven't seen it, so let's get to describing the scenario.

The rest of the Mane Six expresses interest in seeing the human world, and the Humane Six expresses interest in seeing the pony world. But who knows what will happen if more than maybe two from one world are in the other, so they decide to give each visitor a day before they go back and someone else goes through. On the human side, Sunset will be there to help acclimate the ponyborn to being a human before they meet the counterparts to their friends... and themselves, and Princess Twilight will serve the same function ponyside.

I don't want any shipping (outside of canon).

One aspect that I thought would be interesting would be seeing what the mirror has the Mane Six wear, since Princess Twilight's outfit is different from anything we see Human Twilight wear.

Could be a fun little Slice of Life, or something else.

Title: RariJack'd and AppleDashed
Tags: EQG, Comedy, Romance, Applejack, Applejack, Rainbow Dash, Rarity

Sunset has taken her friends to Equestria over the weekend, to experience life as ponies.

Rarity sees the perfect opportunity for a romantic date with her Applejack.

Incidentally, Rainbow Dash also has a date with an Applejack at the same restaurant.

Obligatory mixups and "Applejack-switcheroo" ensues.

Things get really mixed up when pony Rarity and human-turned-pony Rainbow Dash show up too, then get heated when one of them brings up the question why the "other you" isn't dating the "other me"!

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...I imagine if she swallowed the Crystal Heart whole, this could be even more funny:

She'd be radiating all that love and happiness from the Crystal Ponies -- she'd open her mouth to complain, only for a bright pink ball of magic to come flying out. She'd cover her mouth, and an aurora borealis would come out of her nostrils. They'd have to be extra careful to get the heart out.

And of course, can't forget the shield: A snow storm / a herd of wendigoes is approaching, and the Crystal Heart needs to be on its spire - no time for stomach surgery! So poor Ember has to, ahem, sit down on the spire just right, so that the Crystal Heart is properly aligned.

And of course, when the Crystal Ponies celebrate the wendigoes' defeat, their happy emotions cause the heart to surge.

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I'd like to write this if it's still on the table and nobody took it.
I really like Gilda and Scoots so.

Edit: Nevermind
Sorry, got too ambitious

Kindred Spirits

Characters: Starlight, Fluttershy, Angel Bunny
Tags: Romance, Drama

Angel Bunny, while in Fluttershy's body, runs across Starlight. He starts flirting with her. Starlight is very confused.

When it later comes out it was Angel flirting with her, that... doesn't make her feel any less confused.

 
 
 
Actually, "She Talks to Angel" revealed something shocking about Angel Bunny: He's never really had anyone else to talk to other than Fluttershy his whole life.

Not other animals, not other ponies. I guess there is an intelligence / interests / communications gap.

Fluttershy is his only friend. No wonder he gets upset when she suddenly has less time for him.

Let me repeat that. In a world running on friendship, Angel Bunny. Only. Has. ONE. Friend.

And leading up to that episode, with Fluttershy having less and less time for him, he felt like his only friend was abandoning him.

...Yeah, I can see Angel seeing Starlight as a kindred spirit.

If he'd been born a unicorn, he'd have gone and pulled a Starlight by now.

Stand-in Title: The Friendship Chronicles (I don't really have a decent name for this idea )
Main Characters: The Mane 6 and Spike
Supporting Characters: Starlight Glimmer, The Young 6, the Former Royal Pony Sisters, Sunset Shimmer, and Everyone's Extended Families
Tags: Drama, Action, Drama, Comedy, Drama, Romance, did I mention Drama?

Twilight Sparkle has just been crowned the Sole Ruling Princess of Equestria and has founded the Council of Friendship alongside her friends to assist in her rule. But this doesn't necessarily mean that a happy ending has been achieved: there's likely a lot of things that need to be cleared/set up before the idyllic future seen in The Last Problem can come into play.

In terms of time, twilight is the period where morning meets night and night meets morning, a time of change and renewal for each and every day. The same goes for Twilight's time as Princess. The School of Friendship was a good trial run; can she extend her learned wisdom and friendship lessons to the whole world? Well, yeah, obviously, we've all seen it.

But what we didn't see is how they all got there.
Have fun!

The Evolution of Harmony

characters: the Pillars of Harmony, Everyone Else

This is my first idea here, so I hope it's okay

Upon their return to the modern day the Pillars are examining pony and other culture and while they do like it, there are some noticeable changes. Dragons were always gruff and agressive, but now they are even more so. Griffins have taken a real downturn. The pony tribes are now truly one nation. At their time, they were already one of course, but it was new enough it could still end. Not in this era. But the heart songs are new.

So the jist is that due to the number of emotion eating super-predators in Equestria/Equus/whatever the full planet is called species adapted and even physically evolved their behaviors, with some going for less expressive emotion, like with the number of Griffins who's standard attitude is mild annoyance with everything it's hard to bump them all the way up to full hatred to empower Windigos or Sirens or to offer enough love to feed changelings, meanwhile ponies got so hyper in touch with their emotions it's hard to manipulate effectively because they can basically tell. A side effect of that is they're so in tune with their emotions sometimes they are expressed extremely strongly

Prompted by this April Fools thread on /r/MyLittlePony: Derpy and Dinky go through the Mirror Portal. Dinky turns human. But something goes wrong with Derpy... and she stays a horse.

This idea is five years old and gathering dust. I figured this is as good a place as any to donate it to someone who might be able to put it to words. More old ideas might be coming...

A Canterlot Wedding's Requiem
Tags: AU-ish, Tragedy, Dark, Sad, Hurt/Comfort

Alt Route 1 - Chrysalis killed Twilight in the green fire, leaving no one to stop her from marrying Shining Armor and setting the Changlings upon the ponies. Cadence, meanwhile, is still trapped underground, forced to watch everything via the crystals that trap her.

Alt Route 2 - Plays out like normal, seemingly, until Applejack apologizes: Twilight says nothing and continues to do so throughout the episode. She asks Spike a question, then decides to just up and leave, deciding that she no longer has friends.

Odd Chapters are Route 1, Even are Route 2.

Chapter 1 - Last Words (Twilight Sparkle's final moments)
Chapter 2 - Apathy (Twilight is numb throughout the middle of ACW)
Chapter 3 - This Day Reprise (Cadence remains trapped in the caves)
Chapter 4 - No Goodbye (Twilight isn't happy with how things are)
Chapter 5 - Ruse (the marriage goes off without a hitch)
Chapter 6 - Gone (Pinkie Pie discovers that Twilight has vanished)
Chapter 7 - As the Crow Flies (the Changeling invasion from the perspective of a crow)
Chapter 8 - Alarm (the girls can't find Twilight anywhere)
Chapter 9 - Nowhere (same as above, only worse near the end....)
Chapter 10 - Journey (Twilight starts her aimless wandering)
Chapter 11 - Crippled (Celestia is captured, the girls are beaten)
Chapter 12 - Honeymoon Interrupted
Chapter 13 - Broken Night (Luna awakens to the invasion's aftermath)
Chapter 14 - For Want of a Friend (Spike realizes why Twilight left)
Chapter 15 - Deliverence (Luna rescues Cadence)
Chapter 16 - Not Fair (regret runs deep)
Chapter 17 - Insurgence (Luna and Cadence to the rescue)
Chapter 18 - The Search (looking everywhere for Twilight)
Chapter 19 - Act of War (the Changelings are defeated, but at what cost?)
Chapter 20 - Saving Grace (Twilight is found, but will she return?)

Childhood's End
Characters: The CMC, Babs Seed, Pipsqueak, Twist, Diamond Tiara, Silver Spoon, Rumble, and the Other Foals of Ponyville
Tags: Sci-fi, Action, Drama, Violence, Dark

Setting can be at any point in the series timeline.

Equestria is a land of peace and harmony, a land where anything and everything can be solved with kind words and understanding. It was completely unprepared for the Wasps when they swarmed down from beyond the sky.

There had been little time for anything other than confusion and fear when Applejack shoved Winona in with Apple Bloom and Babs Seed down the family Apple Cellar, told them to stay there until she came back. That was two days ago and rations ran low, so the fillies braved the outside...and saw a world overrun by alien entities far smarter than they looked.

The two soon discover that they weren't the only ones left behind, friend and enemy alike joining together as an unknown future stands before them. Can a group of foals be enough to save Equestria? The Princesses and their sisters aren't there to guide them. They're going to have to do this on their own.

(Inspired by Falling Skies)

Idea/challenge for anyone to use/have a go at!
takes place during “cutie re-mark” PT 1 and 2
Anyone is free to use this idea as long as they credit me and Send me the link for the story.

The main part of the idea comes from Having twilight purposely or accidentally take somepony (or other) from one of the alternate timelines back with her to the OG timeline, such as
(eternal night Vr) Rainbow Dash,
(Changeling Invasion succeeds Vr) Fluttershy,
(war against Sombra Vr) pinkie pie

or you could swap use other ponies like…

(changeling invasion Vr) pinkie pie,
(war against Sombra Vr) Rainbow Dash,
(eternal night Vr) rarity
Or…
Maybe use One of the main six from one of the timelines we only got to see a few moments of!
Like the Tirek or flimflam brothers timeline.
Or……
Maybe you could go for something completely different like bringing the villains from those timelines to the OG one.
There can be so many different versions of this same idea with numerous different paths the story can follow, from humor and adventure, drama and hurt/comfort to boot, depending on how the writer views what happened in the episodes and where are you want this to go.