"Magical Mystery Cure" is the thirteenth and final episode of the third season of the Canadian-American animated television series My Little Pony: Friendship Is Magic and the sixty-fifth episode of the series overall. The episode premiered on February 16, 2013 on The Hub. In the episode, the destinies and cutie marks of Twilight Sparkle's friends get switched around, forcing Twilight to create a magic spell of her own in order to correct it. The title itself is a reference to the Beatles' 1967 album Magical Mystery Tour.
An aspect of the episode focused on Twilight Sparkle's ascent to becoming a princess (an event which would also involve her transformation into an alicorn). The Hub heavily emphasized the event while promoting the episode in a coronation-themed advertising sweepstakes campaign, which included a special concert event featuring Miss America 2013 winner Mallory Hagan, and a nine-episode marathon which preceded the episode's premiere.
Twilight Sparkle awakens one morning to find that her friends' cutie marks and duties around Ponyville have swapped: Rarity's creativity in doing Rainbow Dash's weather control causes havoc around town; Rainbow is completely unable to tame Fluttershy's animals, who run wild around her cottage; Fluttershy is barely able to throw Pinkie Pie's parties and cheer up the residents of Ponyville, who are now very grumpy and tetchy; Pinkie has difficulties working on Applejack's farm, where her apple trees are now bare and blackened; and Applejack's dressmaking skills are awful and is forced to close Rarity's boutique. Twilight's friends are unaware of the change, believing that they are following their true destinies despite their ineptitude with their tasks.
Twilight remembers that her mentor Princess Celestia had earlier sent her the notebook of unicorn conjurer Star Swirl the Bearded, believing that Twilight has the skill to make sense of the final, incomplete spell on the last page. However, when Twilight first read the spell, it inadvertently switched around the Elements of Harmony held in her library, affecting their respective bearers. Realizing that she is responsible for her friends' condition and finding no counter-spell to fix it, Twilight goes to cry in her bedroom, blaming herself for her friends' depression and the resulting desolation of Ponyville.
Inspired by her assistant Spike's compassion, Twilight realizes that if she shows her friends their true destinies and reminds them of what they mean to each other, she may be able to reverse the spell. One by one, she shows each of her friends what their true calling is, encouraging them to help each other fix things. Each friend becomes aware of her original life and regains her original cutie mark with help of her respective Element, and Ponyville is quickly restored to normal. Twilight realizes that her friendship with the other ponies is a factor that Star Swirl had not accounted for, and is able to complete the spell. Upon doing so, the Elements worn by her friends activate on their own, engulfing Twilight in a bright light and causing her to disappear.
Twilight awakens again in an ethereal place where she is greeted by Princess Celestia, who congratulates her and declares that Twilight is ready for a new stage in her life. Twilight undergoes a transformation and returns to Ponyville as an alicorn. Her friends are amazed and happily welcome her change, while Celestia announces that Twilight is no longer her student, but a princess who has demonstrated leadership and other positive attributes from her friends during her stay in Ponyville. Twilight becomes concerned that she has no idea what to do now as she is no longer Celestia's student, but Celestia promises that they will all help each other to learn what may come in the future. Twilight is officially crowned in a grand celebration in Canterlot, and she thanks her friends for being there to help her.
On the topic of Twilight's ascension to becoming a princess, writer Meghan McCarthy explained that Twilight had been embarking on a journey since the first episode of the series that would eventually lead to this outcome. McCarthy explained that the title of princess in Equestria has to be earned by sharing their gifts with others, and that "every little girl wants to be a princess, and not everybody can get to be a princess—but you can live up to the ideals that should come along with being a princess." McCarthy noted that, despite Twilight's new role and the new challenges she will face, her personality will remain the same. McCarthy considers the episode as the first part of a story arc that would continue with the two-part season four premiere episode "Princess Twilight Sparkle", which premiered on November 23, 2013.
When asked of what was stopping Twilight from casting the spell, Larson responded that the script "didn't include Starswirl's [sic] unfinished spell" and that "it was heavily altered from his final script."
The episode is primarily a musical. The show's composer Daniel Ingram created seven songs with episode's writer, M.A. Larson who wrote two songs. Ingram wrote most of the songs lyrics for "I've Got to Find a Way", "A True, True Friend", "Celestia's Ballad", "Behold, Princess Twilight Sparkle", and, with assistance from Larson, "What My Cutie Mark is Telling Me". The lyrics for both "Morning in Ponyville" and "Life in Equestria" were written by Larson. Under the title "Find a Way", a full version of the song "I've Got to Find a Way" is included on the album "Songs of Ponyville".
- Morning in Ponyville – Rebecca Shoichet
- What My Cutie Mark is Telling Me – Ashleigh Ball, Andrea Libman, Shannon Chan-Kent and Kazumi Evans
- (I've Got to) Find a Way – Shoichet
- A True, True Friend – Shoichet, Ball, Libman, Chan-Kent and Evans
- Celestia's Ballad – Nicole Oliver
- Behold, Princess Twilight Sparkle – Cast
- Life in Equestria – Shoichet and Cast
On February 9, 2013, The Hub held a "Coronation Concert" in Los Angeles to promote the episode, hosted by Miss America 2013 winner Mallory Hagan. Despite stating that she was more of a Strawberry Shortcake fan growing up, Hagan felt honored to participate in the event since she supported the series' aim to teach lessons about friendship and acceptance, considering it "a great way to show little girls that they can be empowered by trying to reach their goals." The premiere of "Magical Mystery Cure" on The Hub was also preceded by a marathon of previous Friendship is Magic episodes.
Hasbro also released new merchandise later in the year featuring Twilight Sparkle's new princess form.
"Magical Mystery Cure" premiered on The Hub on February 16, 2013. The premiere had the highest ratings on all demographics and outperformed its key competitors, such as Disney XD and Cartoon Network. The show also earned year-to-year time period delivery gains among Kids 2-11 (+111%), Girls 2-11 (+80%), Kids 6-11 (+187%), Girls 6-11 (+177%), Adults 18-49 (+139%), Women 18-49 (+216%), Adults 25-54 (+116%) and Women 25-54 (+184%).
Ed Liu of ToonZone considered the episode felt "rushed and perfunctory", having nearly two separate stories that would have been told better across two separate episodes, and considered that the large number of songs was a contributing factor towards this. While Liu did not consider it a poor episode of the series, he felt the show had done better with emotional conclusions in previous seasons. Daniel Alvarez of Unleash the Fanboy also acknowledged that the musical format took away time from the story element, but otherwise considered it a "very grand episode". The episode, and its composers, Daniel Ingram and Steffan Andrews, received the 2013 Leo Award for "Best Musical Score in an Animated Program or Series".
The revelation that Twilight Sparkle would become an alicorn was announced several weeks before the episode's premiere, though this had been rumored months before based on photos of upcoming toy lines from Hasbro. The "brony" fanbase—which encompasses older viewers who had grown to appreciate the series—had mixed reviews to this announcement, with a significant fraction considering it a "jump the shark" moment for the show. Shaun Scotellaro of the fan site Equestria Daily considered this a normal reaction to any changes to the show by the fans, but considered that because many of the older fans connect with Twilight Sparkle as a bookish nerdy character, changes such as this would be dramatic. McCarthy and others on the production team have further countered these complaints, with McCarthy stating that "What we didn’t want to do was change who [Twilight] is as a character, because she’s certainly someone that everyone’s proud to know and love", while Tara Strong, the voice actress for Twilight, claimed that the episode is "a birth of a new era for Twilight, but not the end of what makes the show so wonderful".
The season 3 finale is part of the "Princess Twilight Sparkle" Region 1 DVD by Shout! Factory which was made available in stores on April 30, 2013. Along with the season finale, the DVD also includes the episodes "Games Ponies Play" (Season 3, Episode 12), "Magic Duel" (Season 3, Episode 5), "MMMystery on the Friendship Express" (Season 2, Episode 24), and "Lesson Zero" (Season 2, Episode 3). It has also been released as part of the complete Season 3 DVD set.