King Xavier's Castle is based on the king's palace from the "Rumpelstiltskin" fairytale.
In an unnamed kingdom, King Xavier rules as monarch while his son, Prince Henry, awaits to be married. When a northern princess, Eva, comes for a visit, they show her around the castle. Cora, a miller's daughter, arrives with a wagon bearing bags of flour. As she carries some into the castle for delivery, Eva passes by and deliberately trips her. With flour spilled everywhere, Cora berates the princess as a foolish child while King Xavier forces her to apologize to Eva, which she does grudgingly. That night, Cora sneaks into a castle party with a stolen gown, where the eligible ladies vie to be Prince Henry's future wife. She earns a dance with the prince, though King Xavier cuts in. He looks down on her endeavor to be higher class when she is just a miller's daughter, but Cora asserts she can spin straw into gold and could have made the kingdom rich. In disbelief over her claims, King Xavier publicly announces that Cora will prove her ability by spinning a roomful of straw into gold and marry the prince, but if not, she'll be executed. Caught in a dilemma, Cora gains an ally in Rumplestiltskin, a wizard who wants her firstborn daughter in exchange for helping her. She asks to learn how to spin gold, and he trains her to focus on anger to draw out magic. The next day, before an audience, she spins gold and accepts Prince Henry's marriage proposal. While trying on her wedding gown, Cora meets with Rumplestiltskin and reconsiders her future is to be with him rather than be a royal. They plan to run away together, but before that, Rumplestiltskin teaches Cora how to rip out a heart since she wishes to take out King Xavier's. From talking with the king, Cora realizes love is a liability that will keep her from obtaining power. She then takes out her own heart and breaks things off with Rumplestiltskin. Several months later, Cora gives birth to a girl, Regina. Before the royal court, she proclaims her daughter will be queen one day. ("The Miller's Daughter")
- The computer-generated set used for King Xavier's castle is recycled from the computer-generated imagery model for the King's castle in "The Price of Gold". This can be seen from the archways and the balcony outside, which have a very similar design. The model is recycled again for the digital set of the Prince Eric's castle in "Ariel", where the archways and the balcony have the same design as Xavier's castle, except for the different colors. The stairs also have a very similar design. The model is used again for the Camelot castle courtyard in Season Five, another courtyard in the king's castle in "The Other Shoe", and the Prince's castle in "Hyperion Heights", which can be seen from the archways and the railing on top of them. ("The Miller's Daughter")
- When King Xavier is in his chambers, "counting his treasure", the book he is writing in (seen upside-down) contains a list of what appears to be the royal family's valuables, their value, number of items, and weight measured in stone. (The kingdom has been having financial troubles, but, as the king puts it, Cora has made them rich again.) It reads:
|[3 illegible words] coins||201||200||34 [obscured]|
|Silver engraved cups||301||40||20 stone|
|Emerald faced earrings||361||10||.2 stone|
|Jasper goblets||406||20||17 stone|
|[Illegible word] Velvet Capes||407||6|
|Golden [illegible word] apples||401||50||200 stone|
|[Three illegible words]||361||9||.8 stone|
|[Illegible word] Blue Velvet gowns||902||2||8.1|
|Saffron eastern elixir||980||80|
|[Illegible word] shell jewelry boxes||9.86||6||9.2 stone|
|[3 illegible words] nest||9.04||1||.4 stone|
|Jasper decanters||9.50||6||2.8 stone|
|Hand brushed silk rugs||9.82||10||9.1 stone|
|Hand engraved wardrobe||9.09||1||9.80 stone|
|[Obscured] carved [illegible word]||6.01||2.5||4 stone|
|[Obscured] thread spindles|
- The headline at the bottom of the adjacent page says "Price family jewels" and mentions "Emerald Rings" and "sapphire and diamond rings". Above the list of family jewels, there is another list, which mentions a looking glass. The rest of the page is illegible.
- King Xavier's coat of arms is an eagle displayed and expanded (wings spread with the wing tips pointing upward). It can be seen on his fireplace and castle banners. ("The Miller's Daughter")
- The purple coats worn by King Xavier's servants are also worn by other servants throughout the series:
- The King's servants in "The Price of Gold"
- The Red Queen's servants in the Once Upon a Time in Wonderland episode "Trust Me",
- The Red King's servants in the Once Upon a Time in Wonderland episode "Heart of Stone"
- King Midas' servants in "Snow Drifts"
- Prince Thomas' servants in "The Other Shoe"
- King David and Queen Snow's servants in "Wish You Were Here"
- The King's servants in "Hyperion Heights"
- Tiana's servants in "The Eighth Witch"
- The dresses worn by three of the dancers at the masquerade ball is the same dress worn by a woman Prince Charming was dancing with at Thomas and Cinderella's wedding in "The Price of Gold". ("The Miller's Daughter")
|Once Upon a Time: Season Two|
|"Broken":||"We Are Both":||"Lady of the Lake":||"The Crocodile":||"The Doctor":||"Tallahassee":||"Child of the Moon":||"Into the Deep":||"Queen of Hearts":||"The Cricket Game":||"The Outsider":|
|"In the Name of the Brother":||"Tiny":||"Manhattan":||"The Queen Is Dead":||"The Miller's Daughter":||"Welcome to Storybrooke":||"Selfless, Brave and True":||"Lacey":||"The Evil Queen":||"Second Star to the Right":||"And Straight On 'Til Morning":|
|Once Upon a Time: Novels|
|Once Upon a Time: Specials|
|"Magic is Coming":||"The Price of Magic":||"Journey to Neverland":||"Wicked is Coming":||"Storybrooke Has Frozen Over":|
|"Secrets of Storybrooke":||"Dark Swan Rises":||"Evil Reigns Once More":||"The Final Battle Begins":|
Note: "Archive" denotes archive footage.