After losing her family fortune, Rarity, along with her best friend Pinkie Pie, turns to piracy to make ends meet. The two of them commandeer a magical airship and kidnap the princess's personal student.
When Princess Celestia learns of Twilight and Applejack's abduction, she doesn't agree to pay the ransom. Instead, she hires the sky's greatest tactical mind, the Daring Swordspony Rainbow Dash, and her sidekick, Fluttershy. Together with Shining Armor, they track down Rarity's ship in order to save Twilight. As the two groups engage in a game of cat and mouse, more dangerous threats slowly bubble to the surface. Aztec Curses, angry gods, and a mysterious figure known only as the Derp Pirate Roberts.
Can be read over here.
Upon a Falling Feather provides examples of:
- Adventurer Archaeologist: Daring Do, as always.
- Anchors Away: How Dash distracts the Falling Feather.
- Casting a Shadow: The Shadowbolts, naturally.
- The Chessmaster: Rarity. And Princess Celestia.
- Clear My Name: Shining Armor has to do this after the Shadowbolts impersonate him and attack Cadence.
- Confusion Fu: How Pinkie Pie fights. It's highly effective.
- Convenient Eclipse: Villainous version. Lampshaded.
- Disproportionate Retribution: The Dread Pirate Derpy is on a hunt for the stallion who stole her muffin. Not, contrary to what some readers thought, an euphemism for her daughter. An actual regular muffin.
- Eldritch Location: The Amaranthine Tempest, a massive storm that's been ongoing for over 1200 years.
- Everything's Better with Spinning: How non-unicorn swords work.
- False Flag Operation: The Shadowbolts disguise themselves as Shining Armor and then attack Princess Cadance.
- A Father to His Men: Rarity and, to a lesser extent, Rainbow Dash.
- Gambit Roulette: Celestia is implied to have orchestrated events to cause the current situation just to bring the mane Six together, and some of them are quite difficult to predict. Among other things, she planted Big Macintosh on Rarity's ship, predicted where Daring and Braeburn were going to be, and Spike stowing away, possibly.
- Humanoid Abomination: The Shadowbolts.
- Idiosyncratic Episode Naming: All the chapter titles form rhyming couplets, In the Style of... a Pirate Song/Drunken Song
- Indy Ploy: Rainbow Dash's specialty.
- Information Broker: The gryphons, since they run the postal service.
- Leaning on the Fourth Wall: Pinkie, of course. For example, when the story finally updated after a long hiatus, she suggests a recap to get everyone up to speed.
- Left the Background Music On: In the beginning of the first chapter, readers may assume the interspersed song lines in italics are just there to set the mood. Until Rarity asks Pinkie to stop singing sea shanties.
- Master of Illusion: Trixie.
- The Mole: Big Macintosh was planted in Rarity's crew by Celestia as part of her plan to defeat Nightmare Moon.
- Mr. Fixit: Flim and Flam.
- No One Gets Left Behind: Rainbow Dash again, although only for her own crew.
- Oh, Crap!:
- Rainbow Dash and Iron Will when they realize the only way they'll get paid for their services is to help fight Nightmare Moon.
- There's one both ways when Rainbow Dash and the others realize that the prisoners they've been tricked into helping free are Rarity and Pinkie, who they helped lock up in the first place.
- Pirate Girl: Upon a Falling Feather has a cast populated entirely by MLP's main and secondary characters, most of whom are female, so several pirates are female — primarily Rarity (a noblemare forced into the position), Pinkie Pie (who embraces the role completely) and Trixie (who has a minor role and mostly acts like herself).
- Plot Coupons: The seven pieces of eight Daring and Braeburn are tasked to find.
- Reading the Enemy's Mail: A recurring plot point.
- Running Gag: Don't call Daring "Miss Do."
- Sealed Evil in a Six Pack: Not only is Nightmare Moon's essence sealed in the moon, but her physical body is sealed aboard the Midnight Moon.
- Shout-Out: Several to The Princess Bride
- Third-Person Person: Trixie and Iron Will retain this trait.
- Tragic Villain: As indicated in the summary, Rarity, who only became a pirate to try and restore her family name and fortune. It's hard not to feel sorry for her when she's caught and facing the gallows.
- True Companions: Rarity and Pinkie, Dash and Fluttershy, Twilight and Applejack
- Whole Plot Reference: To Pirates of the Caribbean, along with some elements of The Princess Bride and Skies of Arcadia.