Alicorns

Princess Ponies, or Pegasus unicorn ponies, are pony characters in the show who have both a unicorn horn and Pegasus wings. They are all styled as royalty, but the show's head writer, Meghan McCarthy, says that the title of "princess" is one that is earned in Equestria.

The regal unicorn sisters


Princess Celestia and her sister Princess Luna are introduced in the first episode in a series of medieval-like drawings with a narration that says there were "two regal sisters who ruled together and created harmony for all the land," and that "the elder used her unicorn powers to raise the sun at dawn. The younger brought out the moon to begin the night." Lauren Faust commented that Princess Celestia was originally supposed to be Queen Celestia, the highest authority, with no parents who outrank her. Her status was changed to "princess" at Hasbro's request. During a flashback in The Cutie Mark Chronicles, Princess Celestia witnesses Twilight's rare magical talents and takes her as a protégée. Faust has suggested that there is more to Princess Celestia than has been depicted of her in the series, and that she wanted to Celestia to be "mysterious and hard to understand".

Princess Cadance
The first episode of the second season introduces Princess Cadence.

Queen Chrysalis
Queen Chrysalis was described in her debut episode's script as "a GANGLY BLACK PEGACORN with a gnarled black horn." She and the other changelings were designed by Rebecca Dart, the main character designer for season two. Rebecca was inspired by the work of manga artists Junko Mizuno and Hideshi Hino after reading the name "Chrysalis", and "figured she should be insect-like." The changelings are referred to as a different species in the show and not as ponies.

Twilight Sparkle
Twilight Sparkle is introduced in the show as a unicorn, and she even calls herself a "regular old unicorn" in A Canterlot Wedding - Part 1, to which Princess Cadance replies "You are anything but a regular old unicorn." According to the show's head writer, Meghan McCarthy, in Equestria “princess is a designation that’s earned, not freely given and though princesses have specific leadership roles in pony society, being one really means 'being a good pony who shares the gifts that they have been given with others.'" Twilight is set to become a princess and gain wings in the episode Magical Mystery Cure.

Other winged unicorns
The show includes other winged unicorns. Crew members of the show have explained these as animation errors. For example, a filly in Twilight's imagination in Lesson Zero has both wings and a horn. Some royal guards in A Canterlot Wedding, Part 1 have both wings and a horn too. There is an illustration showing a winged unicorn mare and an earth pony stallion in the magical tome that the Cutie Mark Crusaders read in Hearts &amp; Hooves Day.