Princess Cadance

Princess Cadance is a Pegasus unicorn pony who is first featured in the season two finale A Canterlot Wedding - Part 1, alongside Shining Armor, her husband-to-be. She is the former foal-sitter of Twilight Sparkle as shown in a flashback, and becomes Twilight's sister-in-law after the marriage of herself and Shining Armor in A Canterlot Wedding - Part 2. Various promotional materials, including a New York Times ad and official episode summaries, state that she is the niece of Princess Celestia.

Development
Lauren Faust was involved in the inception of the story in which a Princess named Cadance appears. At that point in development, she was not designed as a Pegasus unicorn, and Faust was surprised to see her as such; the decision was made after she was no longer working on the show.

Name
Cadence is a musical term of Italian origin meaning modulation, inflection rhythm, or the closing sequence of a musical phrase. The Princess was named after Cadince, the daughter of a Hasbro Studios executive. The original spelling "Cadence" was used by Hasbro in early publicity material and some products, but the later variation "Cadance" is now used exclusively and prominently in publicity material and products. Prior to the episodes' airing, a New York Times ad gave Cadance's full title as Princess Mi Amore Cadenza, mi amore cadenza being Italian for my love cadence.

Wedding invitation
Cadance is first mentioned by Twilight Sparkle in A Canterlot Wedding - Part 1 when Twilight reads aloud the wedding invitation sent to her from Princess Celestia. Twilight is invited to "the wedding of Princess Mi Amore Cadenza and... [Twilight's] brother", Shining Armor. Twilight immediately resents the situation for not being told about it personally by her brother, and doesn't recognize the name "Princess Mi Amore Cadenza". When Twilight gets to Canterlot and confronts her brother about the wedding, he tells her that Princess Mi Amore Cadenza is Cadance, her old foalsitter, and Twilight gleefully calls her "the greatest foalsitter in all the history of foalsitters" then goes on to praise her as "beautiful", "caring", and "kind" in her voiceover of a flashback of her childhood where she is foal-sat by Cadance.

Twilight's flashback
Cadance, as Twilight describes, is caring and kind in the flashback. She greets Twilight with a hug, bandages her and wipes her tears when she's hurt, plays with her on a swing-set, tells Twilight she feels lucky to be her foal-sitter, and does a little song-and-dance with her. Twilight's voiceover says Cadance spreads love wherever she goes, while a brief scene shows Cadance casting a spell that quells an argument between two ponies. Twilight mentions in the flashback that Cadance is a princess.

Impostor Cadance
Immediately after the flashback, Cadance joins Twilight and Shining Armor. Twilight enthusiastically greets her with the song-and-dance from the flashback, but Cadance coldly rebuffs her. Throughout the episode, Cadance raises Twilight's suspicions with her "demanding", "totally insincere", and "rude" behavior, as she tells her friends. She tries to broach the subject to Shining Armor, but Cadance interrupts before they have a chance to talk and takes Shining Armor into another room. Twilight, peeking through the door, sees Cadance casting a spell on Shining Armor, and concludes that she's "downright evil" then runs off. Twilight confronts Cadance at the wedding rehearsal, in front of Princess Celestia and the rest of the attendants, which makes Cadance run away from the rehearsal in distress. Shining Armor explains that the spell Cadance used on him is meant to ease his headaches, and excuses Cadance's behavior as stress from the wedding preparations. Rebuked, Twilight is left alone to regret her accusation and strained relations with her brother in a short reprise of the song B.B.B.F.F. Cadance returns and trods on a toy-like image of Twilight from the song sequence; Cadance at first looks down compassionately at Twilight, but then her eyes shine green, her face becomes cruel and she encircles Twilight in green flames, which pull her into the ground as the scene fades to black and the episode ends.

The real Cadance
The story resumes with A Canterlot Wedding - Part 2. Underground, in "the caves beneath Canterlot", the imposter Cadance taunts Twilight through apparitions in the caves' crystals. She tells Twilight that the caves are the ideal place to keep those who try to interfere with her plans. Twilight attacks the apparitions with blasts of magical energy from her horn, and eventually breaks open a passage to find a scuffed and scared Cadance who almost immediately recognizes Twilight and tells her she's been imprisoned by the impostor Cadance. She does the song-and-dance from Twilight's flashback, proving her identity, and the two ponies hug warmly.

Cadance and her impostor share a song sequence, This Day Aria, with Cadance and Twilight making their way out of the caves while the impostor prepares for the wedding and begins the wedding ceremony. After the song, Twilight and Cadance are confronted by the three former bridesmaids Lyra, Minuette and Twinkleshine, who block their way out of the caves. The scene cuts to the impostor and Shining Armor almost completing their wedding ceremony, when Twilight and Cadance interrupt the wedding, and a brief flashback shows Cadance throwing a small bouquet to distract the bridesmaids. Cadance declares that the impostor is a changeling, and the impostor reveals herself as queen of the changelings, who is named Queen Chrysalis in the episode's script but not on-screen. Cadance charges the queen, but she backs of when the queen threatens to send her back to the caves. Princess Celestia tries to overpower the queen with her magic, but is defeated, surprising everyone, including the Changeling Queen. Celestia sends Twilight and her friends to get the Elements of Harmony, but they are captured by the Changeling Queen's minions and brought back to the wedding hall, where Celestia is imprisoned in a cocoon and Cadance's hooves are glued to the floor.

Love conquers all
Twilight takes the opportunity, when the queen is preoccupied, to free Cadance so she can reunite with Shining Armor, and her magic snaps him out of his trance. Shining Armor tries to perform a spell to repel the changelings, but he doesn't have the strength to repel them. Cadance tells Shining Armor that her love will give him strength, and the two's magic spreads outward and repels all the changelings and their queen off into the horizon.

Twilight and her friends help Cadance put together her wedding, with arrangements meeting her enthusiastic approval, and Shining Armor jokes that Cadance agreed to marry him after he told her she'd be gaining Twilight as her sister. At the wedding, Celestia proclaims that the power of Cadance and Shining Armor's love is undeniable, and pronounces them "mare and colt". The couple look onto the castle courtyard and wave to the cheering crowds, then kiss.

After a wedding reception montage, Cadance and Shining Armor enter their chariot and Cadance tosses a bouquet, which Rarity violently catches. The happy couple then ride off into the night, presumably going on their honeymoon.

Future appearances
Princess Cadance is confirmed to return at some point during the third season as her name was mentioned in the song, "Ballad of the Crystal Ponies", when Hasbro publicly released an episode clip featuring the song during the 2012 San Diego Comic-Con International.

Toys
A "Pony Princess Wedding Castle" featuring a plastic castle, Shining Armor playful pony, and Princess Cadance playful pony, has been released. A large talking Princess Cadance toy that says phrases when you press her cutie mark has also been released.

As part of the Miniature Collection, Princess Cadance is included in a pack with Shining Armor and Twilight.

Princess Cadance will be part of the fifth mystery pack toy wave.

Trading cards
Princess Cadance is listed as possessing a seventh Element of Harmony, Love, in the 2012 My Little Pony trading cards. The element is also listed as Shining Armor's pet.

Gallery

 * Princess Cadance image gallery