- Merlin's Tower appears in the title card for "The Broken Kingdom".
- The words "gemini" and "cancer", the third and fourth astrological signs in the zodiac, are written on the ceiling inside Merlin's Tower. ("The Broken Kingdom")
- The music that plays in Camelot Castle in "The Price" is the same music that is played secondly in the Prince's castle in "Hyperion Heights".
- The computer-generated set used for the castle courtyard is recycled from the computer-generated imagery model for the King's castle in "The Price of Gold", King Xavier's castle in "The Miller's Daughter" and the Maritime Castle in "Ariel". This can be seen from the archways and the railing on top of them, which have a very similar design. ("The Price", "Siege Perilous", "The Bear King")
- The new courtyard in the King's castle in "The Other Shoe", and the courtyard in the Prince's castle in "Hyperion Heights", were both recycled from the CGI model for the Camelot Castle (itself recycled from the other courtyard in the King's castle in "The Price of Gold"), which can be seen from the identical design of the architecture. The area by the stairs in both castle courtyards were also recycled from the Camelot Castle, which can be seen from the almost identical design of the windows and balustrades.
- The Round Table prop was later re-used as the Sultan's meeting table in his palace in "A Wondrous Place". The chairs are also the same. ("The Price" et al.)
- One of Merlin's Books is a facsimile of page 392 of Foxe's Book of Martyrs, a work of Protestant history and martyrology by the sixteenth century English historian and martyrologist John Foxe, published in 1563. The opposite page and two other pages also seem to be taken from the book: While the text mostly illegible, the pages have the same layout as Foxe's book (two columns separated by a vertical line). ("Siege Perilous")
- As Emma and her family are planning to attack, a blueprint of the Camelot Castle is lying on the diner counter. ("Nimue")
- In Arthurian heraldry, King Arthur's coat of arms is depicted as three or (yellow) crowns against an azure or gules (blue or red) background (in thirteenth century manuscripts), or thirteen crowns against an azure background (in later texts). On the show, King Arthur's coat of arms is a single yellow crown surrounded by four yellow sea-wyverns against a red background (note that there is also a version with a red crown and red sea-wyverns against a yellow background). A sea-wyvern is a legendary creature with a dragon's head and wings, a reptilian body, two legs, and a fish tail. It is the sea-dwelling variant of the creature known as a wyvern. ("The Dark Swan" et al.)
- The seats around the Round Table carry black and white versions of the coats of arms of King Arthur and his knights. While a few are original to the show, others are taken or adapted directly from Arthurian heraldry:
- Sir Kay's coat of arms from the legend, which shows two keys back to back; even though Sir Kay has a different coat of arms on the show. ("The Price")
- Sir Percival's coat of arms from the legend, which is fenced with crosses However, on Once Upon a Time, Percival's actual coat of arms (a lightning bolt against a red and blue background) is from the cover of the band's double live album Steal Your Face (1976). ("The Price")
- A modified version of Sir Beloberis' (an obscure knight from Sir Thomas Malory's Le Morte Darthur) coat of arms. The original version is semy (covered with small objects, spaced in a regular pattern) of crescents crest with three bends (a band running from the bearer's right side corner of the shield to the bearer's left side). The show's version has fewer crescents, there are no bends, and a sword has been added. ("The Price")
- A modified version of Sir Lionel's crest. In legend, it is semy of molets (stars with straight-sided rays) of six (or five) points, three bends. The show's version has only four mulets and no bends, and additional motifs have been added. ("Siege Perilous")
- A slightly modified version of Bagdemagus' coat of arms. The original contains three sinister (left) gloves fingers upward. The shows version contains dexter (right) gloves instead. ("Nimue")
- A modified version of King Claudas' crest. While the original shows a single pine tree, the show's version contains two different trees. ("Nimue")
- The skull of a saber-toothed cat is lying on the table in Merlin's tower. The same skull can be seen in the tower when Merlin tethers Nimue to the Dark One's Dagger hundreds of years earlier. ("Siege Perilous", "Nimue")
- A chest covered in rust is sitting on a shelf in Merlin's Tower. It has the same design as the silver chest used by the Evil Queen to store Rocinante's heart in "The Thing You Love Most", a chest which Regina later retains in the Mayor's office. ("Siege Perilous")
|Once Upon a Time: Season Five|
|"The Dark Swan":||"The Price":||"Siege Perilous":||"The Broken Kingdom":||"Dreamcatcher":||"The Bear and the Bow":||"Nimue":||"Birth":||"The Bear King":||"Broken Heart":||"Swan Song":|
|"Souls of the Departed":||"Labor of Love":||"Devil's Due":||"The Brothers Jones":||"Our Decay":||"Her Handsome Hero":||"Ruby Slippers":||"Sisters":||"Firebird":||"Last Rites":||"Only You":||"An Untold Story":|
|Once Upon a Time: Season Seven|
|"Hyperion Heights":||"A Pirate's Life":||"The Garden of Forking Paths":||"Beauty":||"Greenbacks":||"Wake Up Call":||"Eloise Gardener":||"Pretty in Blue":||"One Little Tear":||"The Eighth Witch":||"Secret Garden":|
|"A Taste of the Heights":||"Knightfall":||"The Girl in the Tower":||"Sisterhood":||"Breadcrumbs":||"Chosen":||"The Guardian":||"Flower Child":||"Is This Henry Mills?":||"Homecoming":||"Leaving Storybrooke":|
|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.