These were all collected from the original thread:

Sisterhooves Social (HerrpFace):

If you watch "Sisterhooves Social" Backwards, Rarity enjoys playing with Sweetie Belle, but gets dirty and starts to hate her to the point where her parents take her away.

Friendship is Magic (aka Pilot) (Mercgilado):

If you watch the pilot episodes backwards, it's about a beloved Night Princess having a breakdown in the old castle. Her sister tells her lapdogs to zap her with friendship lasers, but they don't work and she becomes evil. They proceed to run for their lives, proving what bad ponies they are on the way. The Night Princess goes to town to convince the people she's innocent, but gets booed at, so she leaves.

Too Many Pinkie Pies (Baby Boo):

Pinkie Pie watches paint dry while Twilight explosively creates a horde of Pinkie clones, who run all over Ponyville repairing things. Depressed at first, Pinkie cheers up as she leads the clones to a magical pond where they vanish, until she's the only one left -- only to realize to her dismay that she can no longer be everywhere to do every fun thing with all of her friends.

In the epilogue, Twilight cures a bird that's been magically merged with an orange.

A Canterlot Wedding (Drweegee1337):

If you play the Season 2 finale backwards it's about a wedding where Shining Armor uses a spell to pull changelings into Canterlot. The changelings free ponies from green cum gak and Chrysalis repairs Celestia's horn. Then the real Cadence kidnaps Twilight and takes her into the caves beneath Canterlot. Chrysalis pulls Twilight out of the caves and proceeds to replace Cadence. The Mane 6 goes home and Twilight recieves a hyper late invitation to the wedding.

The Crystal Empire (The Grey Pegasus):

Now if you watch the Season 3 premier backwards, it's about the Mane 6 on a mission to hide the Crystal Heart (which is apparently protected or something by Sombra) and distracting the locals with a fair, which also happens to put the Crystal Ponies in comas through exhaustion of having so much fun. And maybe a case of depression too. Because the Crystal Heart got stolen. In the end, it's revealed that it was Celestia and Luna's plan all along, and they wanted the Crystal Empire gone.

Cutie Mark Chronicles (Baby Boo):

During a hug party at Sugarcube Corner, Rainbow Dash tells about the time she lost her cutie mark doing a Sonic Rainboom. The Mane Six disperse all over town, but the Crusaders chase them down to hear the stories of how that same Rainboom erased all of their cutie marks and left them uncertain of their purpose in life.
The Crusaders get covered in tree sap and clean themselves off with some ziplining.

The Ticket Master (Revenant Wings):

Twilight and her friends come back from a night on the town after recieving six tickets to the Grand Galloping Gala. However, eventually, Twilight decides she doesn't want to go to the Gala and has Spike send the tickets back. However, Celestia insists that Twilight and at least one of her friends must go, so Twilight begins to become stressed over having to choose which pony goes with her.

The other five ponies try to convince Twilight to give them the ticket through such methods such as Pinkie Pie leaving her alone for a little while, Fluttershy messing up Twilight's library, Applejack taunting Twilight with food, Rarity destroying Twilight's dress she was going to wear to the Gala, and Rainbow Dash drying Twilight off after a rainstorm.

Eventually the ponies decide it's better to talk to Twilight about why they want Twilight to take them with her. Fluttershy dreams of scaring away all the birds and animals that are there before eventually leaving in disgrace. Rarity dreams of declining Prince Blueblood then flirts with every other guy at the Gala before leaving them all wanting her. Pinkie wants to party. Rainbow Dash wants to hang out with the Wonderbolts then wow the crowd by one-upping them and showing off. Finally, Applejack states that if she goes she'll lose too much money and that Granny Smith's hip will fail, Big Macintosh's plow will get ruined, and the farm will go into disrepair.

Twilight eventually decides going to the Gala will be too much of a problem and a hassle with her friends, and sends a letter to the Princess respectfully declining the invitation and sends the tickets back. To celebrate, Spike vomits up the perfect apple, and Twilight helps Applejack take the apples from the barn to put them back on the trees.

Return of Harmony (PurpleFire135):

If you watch return of harmony backwards it's about a group of six gray ponies, who after being introduced to Discord, lord of chaos, and learning the magic of disharmony, decided to go play in a maze and become friends. After that they attacked Celestia, ruler of order and harmony. Discord even came to help, but when they tried to defeat her, they accidentally hit Discord and he turned into stone and they forgot everything about him. Oops.

Dragonshy (veryoriginalponyname):

If you watch Dragonshy backwards, it's about a dragon who come to live in a cave near Ponyville, only to have Fluttershy yell at him for no reason and cause him to become depressed. The other ponies try to cheer him up, but he just continues to mope in his cave. Eventually they give up and go home, and now are forced to deal with smoke pollution caused by his depression.

Thanks a lot, Flutterbitch.

May the Best Pet Win (veryoriginalponyname):

If you watch May the Best Pet Win backwards, it's about an a-hole tortoise who pins a rock on Rainbow Dash's wing and abandons her in a gorge. Some wierd reverse rockslide frees her, and she gets back at the tortoise by being a bitch to him for the rest of the episode.

A Friend in Deed (veryoriginalponyname):

If you watch A Friend in Deed backwards, Pinkie Pie ruins a beautiful relationship between two elderly donkies and continues to pester and annoy Cranky untill he becomes a bitter, angry curmudgeon and leaves town.

Mysterious Mare-Do-Well (GAPDashie)

If you watch MMDW backwards, Rainbow Dash gets frustrated at her friends, who for some reason are all dressing in identical superhero costumes and causing a series of disasters in Ponyville. She goes on a crusade to outdo Mare Do Well in fixing them. After instantly repairing a shredded hot air balloon in mid-flight, Dash finally succeeds in running the superhero out of town, and throws a filly down a well to celebrate.

Boast Busters (Baby Boo):

Twilight Sparkle steals mustaches from Spike, Snips & Snails, then pulls a sleeping Ursa Minor away from its mother, takes away its milk, and sets it down to attack Trixie, who has come running up in a puff of smoke. Fortunately, Snips & Snails are able to lead the Ursa back to its cave.
The next day, Trixie fixes Rarity's mane, saves Rainbow Dash from a windmill, and unties Applejack before telling the story of how she brought an Ursa to Hoofington. Twilight gives Spike another mustache, just so she can take it away again.

Dog and Pony Show (AA-12Ducky):

A Dog and Pony Show is about Rarity who goes to work a part-time job with the diamond dogs in exchange of paying them with truckloads of gems.
The dogs manage to keep Rarity's attitude in check by worsening the work conditions but in the end she proves too much to them and is returned much to her annoyance.

MMMystery on the Friendship Express (Resda):

Pinkie Pie, er, produces a cake made up of a mishmash of various desserts for Princess Celestia. But three other bakers, fascinated with the cake, demand to break it up into its base components and discover what makes it so delicious. So they take it onto a train, where they end up with four partially-complete desserts.

Twilight and Pinkie play with hats as Fluttershy, Rarity, and Rainbow Dash are wrapped up in a fantasy about how they could magically turn Pinkie's cake into a complete dessert, all while picking up bits of clutter they left in random parts of the train.

As the train passes through a tunnel, three of the desserts are magically whole, leaving only the cake incomplete. Pinkie jumps to conclusions, assuming that the other bakers have some sort of baking magic, all the while constructing impossible scenarios for them to fix her cake while she took a nap. In the end, the cake mysteriously constructs itself, and Pinkie collapses out of pure shock.

As the train heads back to Ponyville, Pinkie Pie becomes increasingly paranoid of the others, but when they finally arrive at the station, the other bakers leave with their prizes, and Pinkie enlists Big Mac's help to present the cake to Mr. and Mrs. Cake. The other main six stick around for a while, but end up leaving one by one out of frustration.

Mr. and Mrs. Cake accept Pinkie's offering, nervously at first, but eventually look on the cake with pride.

Fade to black.

I figure if this is a thing that is going to happen, it would help to have a jumping-off point. Here would be a good place to collect the revised summaries for reversed episodes, so that people can keep track.

Note that these summaries were made up as part of the joke/game in the original thread, and most were written before the idea of making a real story series came up. Writers for the Backwards series needn't take any of the above as absolute, just as springboard ideas for the kind of 'backwards' plotting involved.

1172342
Agreed. But at the very least it gives us a place to start!

I came up with an reversed synopsis for "It's About Time" after watching the episode. Here goes!

Spike, Pinkie Pie and Twilight are cosplaying Metal Gear Solid characters inside of the Star Swirl the Bearded Wing (since that's obviously the best place to sneak around).

Spike comes down with a stomach ache, and Twilight's initial concern is resolved when Pinkie says that it's a problem for Future Twilight to deal with.

This gives Twilight the idea to troll herself by leaping a week into the future using a time spell, to smack herself in the nose. She then tells Future Twilight all about her paradoxical discovery before reappearing inside the Star Swirl the Bearded Wing.

After a moment to realize how stupid her cosplay is, triggered by Celestia commenting on her manecut as she walks backwards through the Star Swirl the Bearded Wing, she decides to cause a world-ending disaster. Of course, she lacks the power to do so, and enlists Pinkie Pie and Spike to help her look for a spell to use.

She looks at herself in the mirror once more, lamenting the destruction of her reputation - a lament that is justified when the guard escorts the trio out of the Star Swirl the Bearded Wing, locks it up, and backs away from her, pretending he never saw her.

Fearful of humiliation, she sneaks around the guards by climbing tapestries and lurking through hallways before escaping out the window, playing statue and escaping onto the train to Ponyville.

At some point Spike gets the idea to vomit up the ice cream he had eaten in an effort to stop his stomachache. He ends up putting the regurgitated ice cream in a cone, but he doesn't know where the trash can is and ends up carrying it the whole time.

Twilight uses her research to enact her doomsday plan, monitoring everything in order to figure out her next move. Pinkie Pie finally takes off Twilight's eyepatch and throws it into the fireplace, agreeing that Metal Gear Solid is a stupid thing to cosplay. Twilight finds something bright and interesting in her telescope that inspires her to make a few calculations. All the while, Spike is vomiting ice cream into empty ice cream jugs, trying to stem his stomachache. Pinkie Pie has enough of all the weirdness and leaves the library.

Some time later, inside Madam Pinkie's tent, Pinkie Pie uses her gypsy magic to levitate a broken flowerpot off of Twilight's head and tell her that she got a cool birthday present last year.

Twilight, in frustration, returns to the library, where Rainbow Dash is waiting for her. She admires her manecut in the mirror, and Spike uses a fire spell to steam Twilight's mane down from its spiked look, angry at Twi's insistence upon wearing it that way.

Spike's efforts make Twilight go catatonic with shock, inciting him to try tickling her chin and RD to try scaring her with a mouse. Eventually RD leaves and Spike gives up, vomiting more ice cream into containers.

Twilight paces the floor, still trying to enact her doomsday plot. Spike is convinced that Twilight is delirious from an infection based on the cut on her cheek, and utilizes a burning lost dog flyer as a way to try to cauterize the wound. Twilight dashes off, struck with an idea from the Lost Dog flyer, as Spike goes to sleep off the remains of his stomachache.

Later that day, Twilight returns, ball in her aura, with CERBERUS, HELL BEAST OF THE UNDERWORLD in tow. If that doesn't cause a doomsday scenario, nothing will!

But Cerberus isn't cooperating. Twilight tells Pinkie to take away his ball and hide it, and encourages Fluttershy to pet it the wrong way, causing Cerberus to fly into a rage. But the ensuing panic scares off Cerberus, and he hides behind a house.

Meanwhile, RD decides to take an unnecessary trip to Manehattan. This inexplicably gives Twilight the idea to bring disaster about Equestria herself, and writes a checklist of things that could bring about said disaster, enlisting her friends to do her evil work.

Pinkie flails about as Rainbow Dash returns, and Twilight makes an announcement to Ponyville that disaster will surely strike and that everyone should ignore any comments they hear about Twilight being a sissy pony who cosplays Metal Gear Solid. Pinkie decides to throw a party to celebrate Twilight's evil victory, and enlists Fluttershy's help in taking party supplies.

Satisfied with her work, she returns to the library, only to get booped in the nose by her past self, and hear a spiel about how she discovered time travel.

Twilight shrugs and moves on with her day, agonizing over what evil to put on the agenda for next month. The rhythmic tapping of her footsteps is enough to lull Spike to sleep, where he dreams of leading Rarity away from an ice cream house.

End Scene.

1172524
Absolutely, and it's a good idea to collect the synopses here. Just wanted to let anyone who joins later know that this is brainstorm material, not like formally hammered out before they got here.

Hehehehe, so there would also be a bit in there where Dash helps AJ remove the patches from cracks in the dam...man, these mares just have it in for Ponyville.

1172563 I approve of the idea to collect them here. And you're write, those mares do have it in for Ponyville: backwards, it's like the good guys are bad and the bad guys are good!