Sunset Shimmer

Sunset Shimmer is a female unicorn and the main antagonist in My Little Pony Equestria Girls.

Develoment
unset Shimmer resembles the G3 Earth pony Sunshimmer in pony design and name.

An image of human Sunset Shimmer that appears on the back of the Equestria Girls Sunset Shimmer & Twilight Sparkle doll release's packaging was posted online in mid-March 2013.

On March 19, 2013, Meghan McCarthy was asked "Is Sunset Shimmer going to be a Season 4 storyline? The fact that her backstory seems like a show plot" and responded "Nope."[4] On April 1, 2013, McCarthy wrote as part of an April Fools' Day joke that My Little Pony Friendship is Magic season four episode five would be titled "The Student Becomes the Teacher: The Return of Sunset Shimmer".[5]

Depiction in the film
Sunset Shimmer appears in the film My Little Pony Equestria Girls as the main antagonist. She is a pony who steals Twilight Sparkle's element of magic crown, and in a tussle with Twilight, the crown is thrown into a mirror that acts as a portal to another world, which Sunset goes through to get the crown.

Celestia reveals that Sunset was a former student of hers, who began her studies not long before Twilight did. However, when she did not get the things she desired as quickly as she'd liked, she turned cruel and dishonest, eventually deciding to abandon her studies and pursue her own path.

In this other world, Sunset has been living as a human for some time, and has won Canterlot High's Princess of the Fall Formal three times in a row. She discovers that Fluttershy had found the crown and turned it over to Principal Celestia, much to Sunset's annoyance, as she wants to use the crown for its magical properties as to create an army of teenagers to invade Equestria through the portal. Principal Celestia believes the crown is the same as the prop used as the award for the Fall Formal, but is unaware of its true origins. Learning that Twilight will be competing against her for the title of Princess of the Fall Formal, Sunset tries many ways to hinder and humiliate Twilight, such as releasing videos of Twilight struggling to get used to the human world taken by Snips and Snails, and doctoring photos to frame Twilight for ruining the dance decorations. But her friends help to counter these ploys by improving Twilight's reputation and Flash Sentry, Sunset's ex-boyfriend, proves that Twilight is innocent.

At the Formal, Twilight is named the Princess and given the crown, but Sunset has Snips and Snails kidnap Spike and threatens to destroy the portal to Equestria unless Twilight gives her the crown. When Twilight refuses to give her the crown, stating that her being stuck would be worth stopping Sunset, and her friends congratulate her bravery, Sunset snaps and attacks her. The others aid Twilight in keeping the crown away, but Sunset manages to don the crown. However it did not go as she expected, as she began to shed tears as her darker side takes over and transforms her into a demonic shape. She transforms Snips and Snails into minions with similar appearances, and quickly uses her newfound powers to destroy part of the school and brainwash the other students at the school. She then reveals that she never intended to destroy the portal, and will use her teenage army to conquer Equestria. Twilight is able to evoke the Elements' magical powers when her human friends move to defend her from Sunset Shimmer's attack, temporarily transforming the six into pony-like humans and wielding a power through their friendship that is able to exorcise the demonic form from Sunset, Snips, and Snails, and revert the rest of the students to normal.

As everyone recovers, a repentant and traumatized Sunset is reduced to tears and asks for forgiveness to which Twilight replies by asking her friends to become Sunset's new friends, something she hasn't had before. Sunset, Snips, and Snails are then tasked by Vice Principal Luna with rebuilding the part of school that they had destroyed during their attack.