The episode was co-written by co-creators Adam Horowitz and Edward Kitsis, while Greg Beeman directed. Actress Kristin Bauer van Straten was cast at the last minute and guest starred as the sorceress Maleficent, a character from Disney's 1959 animated film Sleeping Beauty. Mary Margaret's (Ginnifer Goodwin) loft as well as most of the interior shots of the episode were filmed in Vancouver, while many exterior shots were shot in nearby Steveston, British Columbia.
Regina looks through the book of fairy tales; she discovers that the last few pages are torn out. She confronts Henry, who lies and says that the pages are missing because it is an old book. Believing that Emma will try to take Henry away from her, Regina encourages Emma to leave town and mentions that Henry is in therapy. Regina meets with The Daily Mirror editor, Sidney Glass, who has run a front-page story about Emma's auto accident which portrays Emma in a poor light, but tells Regina that he has found very little of interest in Emma's past.
Henry tells Emma that he has a plan for them to break the curse, called "Operation Cobra". The first step is to identify which characters from his book each of the Storybrooke residents are, as no one in Storybrooke can remember their past. Henry explains to a skeptical Emma that she is the daughter of Snow White and Prince Charming. Concerned about Henry, Emma goes to see his therapist, Archie Hopper. She is willingly given Henry's file, only to be arrested when Archie claims she stole it. Regina unsuccessfully tries to use the incident to divide Emma and Henry. Emma then goes to Regina's house and attacks Regina's apple tree with a chainsaw, provoking another confrontation.
Back at the inn, Granny apologetically kicks Emma out, telling her they have a no-felons policy. Regina calls Emma and suggests that they meet at Regina's office to make peace. Once there, Emma tells Regina that she does not plan to take Henry away, but that she is worried because Henry's belief that the Storybrooke residents are fairy-tale characters is "crazy." Henry appears in the doorway; he has overheard Emma and runs away, hurt. Regina acknowledges that she knew Henry would arrive just in time to overhear Emma. Mary Margaret persuades Emma to stay in Storybrooke on Henry's behalf. Emma tells Henry that she thinks the curse is crazy, but that does not mean it is not true. She also tells him that in order to break the curse, they must keep Regina off their trail by making her think that they don't believe in the curse.
As Regina tends the apple tree, Mr. Gold appears and tells Regina that he has just seen Emma and Henry walking together. He offers to help Regina get rid of Emma, for a price. Regina says that she is not in the business of making deals with him anymore, and Gold acknowledges that she had made a deal with him in the past to procure Henry. He asks Regina how she chose the name Henry; she does not answer. She questions him about Emma's past, and he is equally evasive. As Gold walks away, Regina gives him a meaningful stare, suggesting that she suspects that Gold remembers their lives in the Enchanted Forest.
In the characters' pasts
At the wedding of Snow White and Prince Charming, the Evil Queen announces her plan to cast a terrible curse on everyone. She goes to see Maleficent, to whom she had traded a Dark Curse. Maleficent refuses to return the curse, but the Queen defeats her in a magical battle, taking the scroll. She lets Maleficent live, stating that Maleficent is the only friend she has. Later in the forest, the Queen assembles a number of dark creatures. She demands a lock of hair from each of the assembly in order to cast the curse, and sacrifices the heart of her prized stallion to complete the spell. The curse, however, fails.
To find out why the curse failed, the Queen turns to Rumpelstiltskin, who had originally given her the curse. Rumpelstiltskin offers to help the Queen if, in turn, she makes him a wealthy and respected person in the new world and promises that in the new world she will do anything he asks so long as he says "please." The Queen agrees, reminding him that in the new world, they would have no recollection of their agreement. Rumpelstiltskin then tells the Queen that she must cut out the heart of the thing she loves the most and use it to complete the spell. The Queen protests that what she loved most died because of Snow White, but Rumpelstiltskin suggests that there is something else the Queen also loves. He also tells the Queen that he has told Snow White and Prince Charming that their unborn daughter will be able to break the Queen's curse.
On returning to her castle, the Queen is distraught over what Rumpelstiltskin told her. She confides in her valet, who is revealed to be her father. Knowing he is the thing the Queen loves the most, her father tries to dissuade her from her plan, saying that she could still find love again. Appearing to be persuaded, the Queen pulls her father in for an embrace, then takes out his heart. Alone in the forest, the Queen uses her father's heart to complete the Dark Curse. As the curse takes shape, she lays a black rose on her father's grave. The headstone bears the inscription "Henry, Beloved Father."
As with the pilot, "The Thing You Love Most" was co-written by series co-creators Edward Kitsis and Adam Horowitz. Smallville veteran Greg Beeman served as director. The episode focuses on the rivalry between Emma and Regina, as each believes they know what is best for Henry. In an interview with TV Overmind, actress Lana Parrilla explained that viewers would see a "vulnerable" side of Regina/The Evil Queen in this episode. Says Parrilla, "What I’ve been trying to show is not the hatred for Snow White, but where it derives from. It’s not so surfaced. That brings a vulnerability to the character. You’ll see into her history and that exposes her in a very vulnerable way as well." As for Regina's troubled relationship with Henry, Parrilla noted that "she may have a cold heart, but I think she really, genuinely loves her son. She doesn’t think of him as an adopted son, she thinks of him as her son."
In September 2011, The Hollywood Reporter reported that Kristin Bauer van Straten would be guest starring as Maleficent, a character from Disney's 1959 animated film Sleeping Beauty. She was cast at the last minute, which she felt made her performance more instinctual because of the lack of prep time. The actress described Maleficent as being the Evil Queen's "frenemy," as each has been "kind of helping [the] other and playing this chess game for years." Bauer van Straten noted the similarities between Once Upon a Time and her HBO series True Blood character Pam, and said that she enjoyed the "evil-bitch typecasting". She added that the elaborate purple costume helped her get into character, making her feel "slightly evil."
"The Thing You Love Most" is the first episode to feature Mary Margaret's loft, which is filmed on a small sound stage in Vancouver; most of the first season's interior shots are also filmed in the city, while many exterior shots are of nearby Steveston, British Columbia. The production team led by set decorator Mark Lane and production designer Michael Joy designed the residence to seem "locked in time a little bit, so there's not a lot of new stuff." They included working class antiques such as a Hoosier cabinet, an old gas stove, and a Bakelite radio. The loft was meant to be located above a store and near a lumber mill and water, so the crew also designed it to feel like a fish cannery.
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