There is a Halloween Costume Contest and all members of Mane Seven are participating, but someone wants to win so badly that they are removing the competition. Fluttershy of the Equestria Girls franchise has gone dressed as Jem, the star of Jem and the Holograms franchise and now has been left in bound and gagged in some closet at Canterlot High.

Thanks to  nightwing1975 for the image.

Fluttershy is a character from the My Little Pony franchise and one of the main characters in My Little Pony: Friendship is Magic who appears in Equestria Girls. She first appears in the trailer when Twilight Sparkle is eating at the table. She also appears in the second trailer, carrying Angel the bunny, a red jay, and a "puddy tat" with a blue bow. The human version of Fluttershy has pink eyeshadow, unlike her pony version. Fluttershy is the element of kindness.Jem

In My Little Pony: Equestria Girls, the human Fluttershy is first seen being bullied by Sinset Shimmer. After Twilight sticks up for her, they introduce themselves to each other. Fluttershy acts as shyly as her pony self did when she first met Twilight, and like her pony self, opens up once she sees Spike. Fluttershy tells Twilight that she found her crown outside Canterlot High and took it into Principal Celestia.

She later joins Twilight in the cafeteria at lunch time, explaining how things work at the high school, mentioning all the different cliques and that Sunset Shimmer rules them all. After Twilight is made a fool of by videos of her using the library's computers (filmed by Snips and Snails at Sunset Shimmer's behest), Fluttershy comes to help her, alongside the rest of the human mane six. At this point, it is revealed that the five had been driven apart by the machinations of Sunset Shimmer. Fluttershy particularly dislikes Pinkie for ruining her silent auction for the animal shelter by bringing noisemakers. When Twilight shows them that Sunset Shimmer is responsible for everything, they reconcile, and help Twilight become Princess of the Fall Formal.

Jem / Jerrica Benton (voiced by Samantha Newark, singing voice recorded by Britta Phillips) – Jem is the leader of the Holograms where she provides the lead vocals. She is the alter-ego of Jerrica Benton, owner of Starlight Music and a foster home for girls known as "Starlight House" (later called "Starlight Mansion"). Jerrica Benton inherited both Starlight Music and Starlight House from her late father, Emmett Benton. Using the power of Synergy, a powerful computer with holographic capabilities, Jerrica can become Jem by touching her special star-shaped earrings (the "Jemstar earrings"). Most stories of the series consist of Jerrica hiding her identity from others, especially Rio Pacheco, her long-time boyfriend. Synergy's holograms are integral to maintaining the illusion that Jerrica and Jem are two different people. Jerrica tends to compartmentalize her life in some respects and even occasionally shows jealously toward the alter-ego of Jem she created.