Alicorn

Alicorns are pony characters in the show and other material who have both a unicorn horn and pegasus wings and, depending on the depiction, also have earth pony power. They are styled as royalty. They are referred to as princess ponies in Hasbro's toy line, as Pegasus Unicorns in Little Brown's book Mini Pony Collector's Guide, and, once, as pegasus unicorns on Hasbro's My Little Pony Facebook page. Meghan McCarthy, the show's head writer, says that the title of "princess" is one that is earned in Equestria. The third season episode Magic Duel marks the first use of the term "Alicorn" in the series, and in Magical Mystery Cure the term is used for the first time to directly refer to winged unicorns, previously referred to as unicorns in earlier seasons' episodes Friendship is Magic, part 1 and A Canterlot Wedding - Part 1.

Regal Sisters
Princess Celestia and her younger 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 eldest 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 later changed to "princess" at Hasbro's request. Faust has stated that Celestia embodies the traits of all three pony kinds: earth, pegasus, and unicorn.