LINK TO PART 2: https://www.derpibooru.org/2182301

Part 1 of a two-part request from ‘superfun’. Enjoy!

Hundreds of moons ago, a group of dimension-hopping Equestrian Unicorns led by Star Swirl the Bearded created a unique type of magic spell that causes any sentient being to take on the mind of either a cat or a dog after they visited a dimension populated by humans who wanted to kill them for being ‘unnatural creatures’. Unfortunately, the spell only ended up being used once before the scroll it was written on was blown away by a sudden gust of wind and ended up being blown into a woodland area outside the city of Canterlot. Years later, at the Starswirl Music Festival, Rainbow Dash comes across the scroll while walking around the festival grounds and (upon recognizing the text as Equestrian) decides to show some of her friends. Coming across Rarity, Twilight Sparkle, and Sunset Shimmer, who are hanging out in a rather desolate area of the festival, Rainbow shows them the scroll and Sunset confirms it to be an old spell from her native realm. Wanting to have a little fun, the girls decide to cast the spell just to see if it would affect them, electing Rainbow Dash to read it out to them given that she was the one who found it. Giving another look at the text, Rainbow tells her friends that, for some reason, the spell requires that the listeners be barefoot when it is being cast. The other three, however, don’t seem to mind much (though Rarity has concerns that her pedicure will get messed up) and proceed to remove their shoes and socks, leaving them standing in bare feet on the grass. Once that is done, Rainbow begins to read the spell out loud to her friends. However, what she fails to notice is that the spell seems to be actually affecting the three girls by way of their now green-glowing geodes. Their minds and expressions go blank (barring the small smiles tugging at their lips), they suddenly take on green, cat-like eyes, their bodies freeze up in place, and their thoughts suddenly turn to making their ‘mistress’ happy by becoming good, well-behaved animals…..

Once Rainbow finishes the spell (still thinking that it did nothing), she comments to her friends how lame it sounded, but quickly notices their blank expressions when she looks up at them. Snapping her fingers to get their attention when they don’t respond to her, the rainbow-haired jock gets a nasty surprise as her friends collapse onto all fours and let their new bewitched minds take hold of them. Rarity and Sunset are now acting like cats while Twilight is acting like a dog who (surprisingly) doesn’t start barking at her cat-minded friends. As Rainbow watches the whole scene unfold before her, she starts to grow concerned when she notices that none of her friends’ normal personalities and sentience is showing through in their spellbound state, fearing that she has effectively turned her friends feral. Thinking up a solution, she whips out her phone and starts texting Applejack and Pinkie Pie to meet her at the group’s RV, hoping they can help her think up a way to reverse this curse….