"A Canterlot Wedding" is the collective name for the twenty-fifth and twenty-sixth episodes of the second season of the Canadian-American animated television series My Little Pony: Friendship Is Magic as well as the fifty-first and fifty-second episodes of the series overall. "A Canterlot Wedding" was directed by James Wootton and written by Meghan McCarthy. It premiered on The Hub on April 21, 2012, with both parts airing as an hour-long event. In the episodes, Twilight Sparkle learns that her brother Shining Armor will be marrying Princess Celestia's niece, Princess Cadance. Although Twilight becomes excited by the news of this royal wedding and realizes that she was a childhood friend, she begins to have concerns about the marriage when she notices Cadance isn't behaving like the friendly, caring individual that she remembered her to be when she was her old babysitter.
The premiere of "A Canterlot Wedding" was preceded by a major marketing campaign by the channel, which featured interactive content on the network's web site, promotional events, and a print advertisement taking the form of a formal wedding announcement in The New York Times newspaper. The episode debuted to excellent ratings and was positively received by critics, who felt that the hour-long special was highly ambitious for a children's program, and a further justification for the Brony community that the Friendship Is Magic series has developed. The first half of the episode was watched by over 483,000 viewers and the second half was watched by over 475,000.
Twilight Sparkle (voiced by Tara Strong) is surprised to learn that her older brother and Captain of the Royal Guard, Shining Armor (Andrew Francis), is to be married, and that Princess Celestia (Nicole Oliver) has requested her and her friends from Ponyville to help organize the ceremony. Twilight is somewhat resentful, as she has considered Shining Armor as her "Big Brother Best Friend Forever" ("B.B.B.F.F"), yet only coming to learn of the marriage at this late date and the fact that he (Shining Armor) only sent a letter, rather than coming in person. Twilight and her friends arrive in Canterlot, surprised to find that security has been increased, including a magic shield shell cast by Shining Armor that protects the entire city, due to an unknown threat.
Twilight berates her brother for not informing her sooner and only sending a letter, but he apologizes, offering Twilight to be his "best mare". Shining Armor then reveals that he is marrying Princess Mi Amore Cadenza (Britt McKillip), whom Twilight knows as Cadance, her favorite "foalsitter", cheering Twilight up further. However, when Twilight first meets Cadance, she finds the bride to be cold and distant, seemingly having no memory of a special rhyme they had shared when Twilight was younger ("Sunshine, Sunshine"). As Twilight observes the preparations for the ceremony, she further doubts Cadance's purpose, as the bride criticizes every aspect that her friends are planning. Her friends dismiss Twilight's claims as pressure from the upcoming ceremony mounts. She approaches Shining Armor about her concerns, but Cadance interrupts and takes her brother aside, casting an eerie spell on him that she purports to help him deal with the migraines caused by casting the shield spell around the city.
During the wedding rehearsal the next day, Twilight barges in and decries Cadance as a fraud. Shining Armor is furious with Twilight and explains the apparent reasons for Cadance's behavior, and he, Princess Celestia and her friends refuse to believe Twilight's claims, leaving a saddened Twilight alone with Cadance. When Twilight tries to apologize to her, Cadance reveals her evil side, casting a spell around Twilight which transports her underground to the caves beneath Canterlot.
Twilight finds herself in the long-forgotten crystal caves beneath Canterlot. An image of Cadance appears and taunts her, explaining that the marriage will continue without Twilight's interference. Using her magic to shatter a crystal wall, Twilight finds another Cadance waiting there, but the mare is bruised and battered. Twilight attacks her, but the weary alicorn proves that she is the real Cadance by demonstrating their shared rhyme from their youth. Cadance explains she was abducted by the impostor in the castle to marry Shining Armor herself. The two then work together to escape the caves and try to stop the wedding. Meanwhile, the fake Cadance revels in her victory, secretly plotting against Shining Armor and the others ("This Day Aria").
Just before the ceremony is completed, Twilight and Cadance arrive to expose the deception. The impostor is forced to reveal her true form as Queen Chrysalis (Kathleen Barr), ruler of the black shapeshifting insect-like Changelings that can take on the form of any other being, thus vindicating Twilight Sparkle. Chrysalis has been usurping Shining Armor's power, weakening the shield to allow her Changeling army to invade Canterlot and take over Equestria, desiring to feed her armies off the love spread throughout the land. Princess Celestia attempts to stop her but is overpowered and defeated. Celestia implores Twilight and her friends to recover the Elements of Harmony to stop Chrysalis. Though they are able to fight through one troop of Changelings and make their way to the vault where the Elements are kept, they soon become outnumbered, and are surrounded and returned to the Queen as her captives. With no further resistance, Chrysalis blurts out that the others not believing Twilight has led to her overtake of the wedding and declares her victory complete. Twilight uses the distraction to free Cadance so she may be with Shining Armor. Cadance's magic is able to break Chrysalis's spell on the groom, and with Cadance's love and magic, Shining Armor is able to recast the shield at full strength, physically expelling Chrysalis and her army from Canterlot to parts unknown.
Shining Armor, Princess Celestia and the others apologize to Twilight for not believing her, and Princess Celestia commends Twilight Sparkle, for it was her instincts and conviction to them that ultimately saved the day; she is heralded as the one, true hero. The wedding ceremony is quickly rescheduled, with Twilight eagerly overseeing preparations for a much happier and profoundly appreciative Cadance. Shining Armor and Princess Cadance are married, and a celebration ensues, with Twilight as the wedding singer ("Love is in Bloom"). During the ceremony and the reception, Twilight's ingering anxiety of losing touch with her brother is finally put to rest when Shining confesses that he persuaded Cadance to accept his proposal when he mentioned she would gain Twilight as a sister-in-law. Furthermore, just before the couple departs for their honeymoon, Shining thanks his sister for all she has done and the siblings reaffirm their love.
The Hub heavily promoted "A Canterlot Wedding" in the lead-up to its premiere through a "Royal Wedding" advertising campaign. This promotional campaign featured a microsite featuring new games and digital content themed around the episode, previews of the episode posted through social media (including The Hub's pages on Twitter and Facebook), and an advertisement placed in The New York Times' wedding section on April 13, 2012—formally announcing the marriage of Princess Cadance and Shining Armor. Episode writer Meghan McCarthy explained that the ad was placed in the New York Times because the series wanted to "justify something big and crazy and exciting". Actor and wedding aficionado Tori Spelling also made appearances during promotional events for the episodes, including appearances in segments aired on The Hub during the episode. Though she was scheduled to host a "bridle shower" event in Culver City the week before the episode's airing, Spelling cancelled due to pregnancy sicknesses, with Brooke Burke stepping in to take her place.
The episode marks the last time that series developer Lauren Faust had any input. Faust had previously served as executive producer during season one, and as consulting producer during season two. The episode contains three songs written by series musician Daniel Ingram. For "This Day Aria", a duet song by Princess Cadance and Queen Chrysalis in her Princess Cadance form, Ingram wanted to make the song more emotional than previous work he had done for the series. This has since made the song one of the most popular ones, with having reached over 35 million views on YouTube as of September 2016.
Both parts of "A Canterlot Wedding" premiered on The Hub in the United States on April 21, 2012, airing in an hour-long special presentation hosted by Tori Spelling. The episodes were The Hub's highest-rated programs to date in the demographics of kids 6-11 and households, with a total viewership of 483,000 and 475,000 recorded for both parts respectively. Part one saw an increase in Kids 6-11 by 1,047% and Adults 18-49 by 102%, whereas part two saw an increase in Kids 6-11 by 654% and Adults 18-49 by 46%. Driven by the performance of "A Canterlot Wedding", The Hub earned its second-best Saturday rating in the network's history, with an average of 184,000 viewers and 129,000 households watching the channel between 6 am to 12 am.
The episode received largely positive reviews from critics. Todd VanDerWerff of The A.V. Club gave "A Canterlot Wedding" an "A-" rating, considering it to be one of the reasons why he felt Friendship Is Magic was currently one of the best children's programs. VanDerWerff praised its continuing emphasis on themes surrounding the "painful uncertainties of growing up", commenting that a fight scene between the main characters and the Changelings was "as colorful and fun as anything I've seen on any TV program this season", and also praised Daniel Ingram's work on the soundtrack of the episodes—including the "This Day Aria" musical number between the good and evil Princess Cadance, which he compared to the "villain songs" of the Disney Renaissance. He also recommended "A Canterlot Wedding" to viewers who may be skeptical about the popularity of the series.
David Hinckley of the New York Daily News noted that the complex storyline and darker themes seen in "A Canterlot Wedding" would make it appeal just as well to older viewers, and made the episode also feel relatively ambitious for a children's show. Hinckley and Michelle Profis of Entertainment Weekly noted that the episode's timing was also close to the one-year anniversary of the royal wedding of Prince William and Catherine Middleton. Entertainment Weekly writer Hilary Busis, reporting about the "invitation" that appeared in The New York Times to promote the episode, noted that "Having seen it myself, I can concur; the hour-long special is ambitious, absorbing, and thoroughly entertaining, even to those who stopped playing with My Little Ponies [sic] back in the mid-'80s. (Or, you know, never played with them at all.)"
Shout Factory released a DVD compilation titled "Royal Pony Wedding" on August 7, 2012. It contained both parts of this finale along with "Hearts and Hooves Day" (Season 2, Episode 17), "Sweet and Elite" (Season 2, Episode 9), and "The Best Night Ever" (Season 1, Episode 26). It has also been released as part of the complete Season 2 DVD set.