Princess Cadance

Princess Cadance, formally titled as Princess Mi Amore Cadenza, is a Pegasus unicorn(Alicorn) pony who first appearance is featured in the second season's two-part finale, A Canterlot Wedding, alongside Shining Armor, her husband. She was a foal-sitter of Twilight Sparkle as shown in a flashback. Princess Cadance is also Twilight's sister-in-law effectively after Shining Armor's marriage to her. She is a niece of Princess Celestia as stated in a New York Times ad.

Development
Lauren Faust was involved in the inception of the story in which a Princess named Cadence 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 meaning modulation, inflection rhythm, or the closing sequence of a musical phrase. The Princess' name was inspired by that of the daughter of a Hasbro Studios executive. The original spelling 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, which is a mix of Spanish and Italian for "my love cadence".

Cadenza, as well as being the Italian word for cadence, is also a term in music theory that refers to an extended cadence in which a performer plays a rhythmically free, ornimental solo to show off his/her skills while the accompaniment rests.

Abilities
Cadance's special talent is bringing love to others and spreading the warmth and beauty of love and care.

Wedding invitation
Cadance is first mentioned by Twilight Sparkle in A Canterlot Wedding - Part 1 when Twilight declaims 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 responds what she is doing. 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 in a wedding rehearsal in front of Princess Celestia and the rest of the attendants, which makes Cadance run away from the rehearsal. Shining Armor explains that the spell Cadance used on him is meant to heal his migraine, and excuses Cadance's behavior with stress from the wedding preparations. When Twilight is left alone in the rehearsal hall, Cadance enters and stomps a toy-like image of Twilight which is left over from a short song sequence; Cadance first looks down compassionately at Twilight, but then her eyes shine green and she engulfs 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, telling her that the caves are the ideal place to keep the ones who try to interfere with her plans. Twilight attacks the apparitions and eventually breaks a passage to 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 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 impostor's bridesmaids who stand in 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 the queen threatens to send her back to the caves and Cadance backs off. Princess Celestia tries to overpower the queen with her magic, but fails miserably and gets knocked to the ground after colliding magic. Celestia sends Twilight and her friends to fetch the Elements of Harmony, but they are captured by the changeling queen's minions and are 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.

Merchandise
A "Pony Princess Wedding Castle" featuring a plastic castle, Shining Armor brushable, and Princess Cadance brushable, has been set to be released August 2012.

Gallery

 * Princess Cadance image gallery