Flurry Heart

Flurry Heart, also called Baby Flurry Heart or Princess Flurry Heart, is an Alicorn foal and the newborn daughter of Princess Cadance and Shining Armor and the niece of Twilight Sparkle. She makes her debut in the two-part season six premiere of My Little Pony: Friendship is Magic.

Depiction in the series
Flurry Heart is first indirectly mentioned in the season five episode The One Where Pinkie Pie knows, in which Princess Cadance and Shining Armor announce to Twilight Sparkle and her friends that they're having a baby.

Flurry Heart makes her on-screen debut in the season six premiere, her reveal being witnessed by the Mane Six, Princess Celestia, and Princess Luna. Unlike Twilight and Cadance, Flurry Heart is a natural-born Alicorn; Celestia remarks that "the birth of an Alicorn is something Equestria has never seen".

To commemorate Flurry Heart's birth, the Crystal Empire holds a ceremony called a "Crystalling", in which she is presented to the public, and the light and love within the Crystal Ponies makes the Crystal Heart stronger. However, her crying causes the Crystal Heart to shatter, potentially ushering in an eternal winter. During Twilight and her friends' efforts to restore the Heart, Flurry Heart makes things difficult for them by flying all over, teleporting all over the place, and zapping things with her magic.

With the help of Sunburst, the ponies carry out Flurry Heart's Crystalling and restore the Crystal Heart. It is only after the incident is over that Flurry Heart is given her name.

Twilight babysits Flurry Heart.

Magic
As a natural-born Alicorn, Flurry Heart possesses more powerful magic than newborn unicorns. A blast of magic created by her sneeze alone can blast through several ceilings, and her crying shatters the Crystal Heart into pieces. In addition, she can perform multiple consecutive teleportation spells. After the Crystalling ceremony, her magic is more stable and controlled.

Season 5

 * The One Where Pinkie Pie Knows (mentioned as a "baby")

Season 6

 * The Crystalling - Part 1 (debut)
 * The Crystalling - Part 2
 * The Times They Are A Changeling
 * To Where and Back Again - Part 1 (mentioned)
 * To Where and Back Again - Part 2 (cameo)

Season 7

 * Celestial Advice (cameo as cuckoo clock and in photo)
 * A Flurry of Emotions
 * A Royal Problem (cameo)
 * Once Upon a Zeppelin

Season 8

 * The Maud Couple (cameo in photo)
 * Road to Friendship

Friendship is Magic

 * Chaos Theory
 * Tempest's Tale (mentioned)

Specials

 * My Little Pony Annual 2017