Set during My Little Pony: Friendship Is Magic S2 E26 "A Canterlot Wedding Part 2", Once Upon A Time in Canterlot is a My Little Pony Friendship Is Magic is a Fan Animation starring the Ensemble Dark Horse Octavia. The short revolves around Octavia fighting off Changelings during the invasion.
Once Upon A Time In Canterlot has a spinoff animation, Guardian, about Derpy Hooves saving Amethyst and Dinky Hooves from Changelings.
These shorts contain examples of:
- Ambiguously Related: Derpy Hooves goes Mama Bear on changelings that try to hurt Dinky and Amethyst. Dinky is undeniably supposed to be Derpy's daughter, however Amethyst's relationship to Derpy is the one in question. One episode depicted Amethyst and Dinky going to the Sisterhood Social, but their relationship isn't clarified in the short.
- Anthropomorphic Shift: The ponies use a lot of "human poses" while fighting.
- Big Brother Instinct: It's not directly stated that they're siblings, however it is common fanon to depict them as so because they were in the Sisterhood Social together. Guardian has Amethyst trying to run away from Changelings while Dinky rides on her back.
- The Cameo: Spitfire, Soarin', Vinyl Scratch, Fleur-de-lis, and Fancy Pants are all depicted fighting Changelings at the start of Guardian.
- Mama Bear: Derpy does not take kindly to her daughters being attacked by Changelings and proceeds to beat the attackers up.
- Silk Hiding Steel: Octavia may be a prestigious violinist, but she's also quite adept at fighting.