Crystal Ponies

Crystal Ponies first appear in the third season's opening two-parter The Crystal Empire. Crystal Ponies are distinct by their shiny, gradient manes and tails, and most of the time, polygonal reflections in their eyes. Twilight Sparkle blames King Sombra for the Crystal Ponies' lack of a "crystally" coat.

Depiction in the series
The episode's preview features Twilight Sparkle and Spike talking with a Crystal Pony in the Crystal Empire, and she confirms that the Crystal Ponies have been "gone a thousand years". The Crystal Pony goes on to say she remembers nothing of the time before King Sombra's rule, and that she does not "want to remember" anything about the duration of his rule. Twilight Sparkle speculates that King Sombra's spell must have caused the Crystal Ponies to lose the "crystally"-ness of their coats.

The blurb advertising the Shout! Factory upcoming DVD Adventures in the Crystal Empire proclaims that the Crystal Ponies "suddenly appeared in the arctic north of Equestria" alongside the Crystal Empire.

The song Ballad of the Crystal Ponies features the seven main characters preparing for the "Crystal Faire" based on a book they found. They mean to preserve the Crystal Ponies' history for the sake of the Crystal Ponies who are being supported by Princess Cadence's magic. History discovered includes a fondness for jousting, a flag design, the creation of sweets with crystal berries, the operation of a petting zoo with tiny ewes, the playing of a crystal flugelhorn, and an anthem of the "Crystal Kingdom".

Other depictions
Upcoming and leaked toys depict Applejack, Fluttershy, Pinkie Pie, Ploomette, Princess Cadence, Princess Celestia, Princess Luna, Rainbow Dash, Rarity, and Twilight Sparkle with the appearance of Crystal Ponies. A blurb on the Crystal Empire packaging of one such Fluttershy toy states that "FLUTTERSHY has a tea party to make friends with the CRYSTAL EMPIRE ponies—they seem just as shy as her!"

The Adventures in the Crystal Empire DVD cover also depicts the six main ponies with the appearance of Crystal Ponies. While Applejack, Fluttershy, Rainbow Dash, and Twilight Sparkle all have polygonal eye reflections, and in Applejack's case polygonal freckles, Pinkie Pie and Rarity have their usual rounded eye reflections.

Hasbro-licensed translucent Special Edition Crystal Pony keychains of Pinkie Pie, Rainbow Dash, Applejack, and Rarity made by Basic Fun were presented at the February 2011 Toy Fair; Pinkie Pie and Rainbow Dash were released later in the same year, but Applejack and Rarity have not been released.