Mermaids are mythological characters featured in ABC's Once Upon a Time. They are native to the Enchanted Forest, Neverland, and the Wish Realm, and first appear in the first episode of the third season.
Mermaids are based on the species of the same name from the story Peter and Wendy, and the Disney film Peter Pan. They are also based on the species of the same name from the fairytale "The Little Mermaid" and the Disney film of the same name.
Once Upon a Time[]
Before First Curse[]
In the Enchanted Forest, Poseidon makes his mermaid daughter Ursula enchant sailors with her singing voice and lure them to their deaths. When the Jolly Roger passes through, she does as her father asked but stops at the last minute, freeing the men from their trance and allowing them to sail away, but the ship's captain, Hook, remarks that mermaids are "the most dangerous creature in all the seas." No longer wanting to do her father's bidding, Ursula runs away with plans to reach Glowerhaven, a trip made simpler when she is recognized by Hook, who offers to take her wherever she wanted. Poseidon later visits Hook and entices him with squid ink, something that could paralyze Rumplestiltskin, in exchange for taking away Ursula's singing voice with an enchanted shell. Hook decides to tell Ursula about it, who then steals the ink for him instead, only to be taken away by Poseidon. An angered Hook proceeds to trap Ursula's voice in the shell as retaliation against Poseidon. Shattered at this betrayal, Ursula decides she no longer wants to be a mermaid and uses her father's trident to transform her tail into tentacles. ("Poor Unfortunate Soul")
A long time after, a mermaid named Ariel pulls a man, Prince Eric, to safety after he nearly drowns from a shipwreck. Despite falling in love at first sight, she leaves before he wakes up. ("Ariel")
A year later, Ariel hears of the upcoming the upcoming the Under the Sea Celebration in honor of the legendary sea goddess Ursula. She attends in the hopes of meeting Eric with the help of a myth, which states that at the rising the high tide until the next one occurs, merpeople have the ability to walk on dry land. After saving Snow White's life, Ariel and her new friend head to the party. At the Ball, Eric waltzes with Ariel and invites her to join him tomorrow for a traveling expedition. While she discusses the matter with Snow White, the Queen spies on them through a mirror. Upon discovering the mermaid desires to be with Eric, the Queen impersonates Ursula and tempts Ariel with a magic bracelet that will allow her to stay human. As a price, whoever wears the bracelet will take her place as a mermaid. In a misguided attempt to help Snow White escape the Queen, Ariel clasps the bracelet on her so the ex-princess can live under the sea. After learning of the deception, Ariel stabs the Queen in the neck and flees with Snow White. In mermaid form, Ariel swims to meet Eric at the castle balcony, but she is silenced due to her voice being stolen by the Queen, causing Eric to leave without noticing her there. ("Ariel")
At some point, Ariel finds a necklace that allows her to maintain both her voice and human legs as long as she is wearing it. She travels to Agrabah to find Eric, but while in the marketplace, she incurs the wrath of a vendor after she takes a fork from his stall without paying for it. Once the vendor catches up with her, he rips off her necklace as payment for what she took from him, causing her legs to revert to a mermaid fin. The sight of Ariel's tail frightens the man, who calls her a monster, which the Princess Jasmine overhears before paying for the stolen fork and telling him to get out of her sight. The man acquiesces by dropping the necklace and turning tail, to which Jasmine hands the necklace back to Ariel, who puts it back on to restore her voice and human legs. Upon hearing Jasmine needs help from an army to defeat the sorcerer Jafar, Ariel mentions Eric has a navy fleet that she could use. Together, they ride a flying carpet and Ariel eventually spots Eric's navy flag near a tent encampment. Ariel goes to Eric and admits to him that she is a mermaid, which Eric seems to take in stride until he reveals himself to be Jafar in disguise. As Jafar taunts Jasmine about her futile attempts to protect her kingdom from him, Ariel grabs a bottle of dust which she assumes is magical, but before she can give it to Jasmine, the sorcerer teleports her back to the sea. ("A Wondrous Place")
At another time, the Evil Queen goes to Rumplestiltskin's castle to discuss a deal with a particular mermaid. The conversation is cut off when Rumplestiltskin asks her to leave, to which she does. ("Skin Deep")
At some point in time, Alice and Cyrus go swimming with mermaids. ("Down the Rabbit Hole")
After First Curse[]
Using a magic bean to reach Neverland, David, Emma, Hook, Mary Margaret and Mr. Gold travel aboard the Jolly Roger to rescue Henry. As they sail towards the island of Neverland, Mr. Gold mysteriously parts from their group and the ship is soon under attack by a school of mermaids. Regina scares off the horde with fire magic while Emma and Mary Margaret catch a mermaid on a fishing line. Once the creature is pulled onto the deck, an argument ensues about what to do with it. While they are distracted, the mermaid blows into a conch shell to cause an incoming storm, which gradually worsens due to the growing tensions between everyone aboard the ship. Much later, Emma discovers the real reason for the storm, and risks her life to push the group into working together; thus helping to calm the sea. ("The Heart of the Truest Believer")
Fed up with Emma's decision to investigate Pan's claims that Neal is alive, Regina separates herself from the group and runs into Mr. Gold in the jungle. After shaking some sense into him, they team up to fight against Pan. Mr. Gold mentions there might be a way to contain Pan, but alas, the weapon is back in Storybrooke. To find a way to retrieve the item, they go to the riverside where Regina uses a conch shell to summon the mermaid Ariel. As Ariel has the capability to swim between worlds, Regina wants her to go to Storybrooke and bring the weapon to them. To placate the mermaid, she returns Ariel's lost voice. Regina also promises if Ariel goes to Storybrooke, she will find Eric. ("Ariel")
Swimming into Storybrooke, Ariel gains Belle's assistance in finding Pandora's Box, which can help Mr. Gold defeat Pan. They are sidetracked by Pan's minions, John and Michael Darling, who attempt to destroy the box. Later, the two brothers admit they are only following Pan's orders because he is holding their sister, Wendy, prisoner. Belle convinces them that Mr. Gold is their only hope of saving Wendy, which they agree with. Ariel returns to Neverland to deliver the box where she begs Mr. Gold and Regina to rescue the Darlings' sister. Afterward, she returns to Storybrooke and reunites with Eric at the dock. ("Dark Hollow", "The New Neverland")
Before Second Curse[]
Once Regina stops Pan's curse, all the residents of Storybrooke, excluding Emma and Henry, are sent back to the Enchanted Forest. While searching for her beloved Eric, Ariel learns he has been kidnapped by a pirate captain of the Jolly Roger. Believing Hook is the culprit, she confronts him and discovers the ship was previously taken by another pirate named Black Beard. After much searching aboard, Eric is nowhere to be seen. As a trade, Black Beard vows to return Eric if Hook gives up trying to reclaim the ship. Hook refuses, throwing Black Beard to the sharks, as he believes Ariel shouldn't waste her time looking for a lost loved one. An angry Ariel curses Hook for being so cold-hearted before jumping overboard to swim away and continue the search alone, and unknown to Hook, she rescues Black Beard from the sharks. As thanks for saving his life, Black Beard tells Ariel that Eric is on Hangman's Island, which is where she eventually reunites with him. ("The Jolly Roger", "Fall")
During Second Curse[]
In order to weaken Emma's light magic, the villainous Zelena disguises herself as Ariel, as she knows of the mermaid's prior run-in with Hook, during which he ruined her chances of finding Eric. Fabricating Eric's death, "Ariel" mourns the loss as a guilty Hook confesses what he did a year ago in the Enchanted Forest. As proof he still believes in love, she asks him to swear on the name of the woman who broke his heart. No sooner than the words "Emma Swan" come out of Hook's mouth, Zelena curses his lips; ordering him to kiss the Savior and strip her of her light magic. Rather than tell Emma the truth about what Zelena has done to him, Hook says Ariel already left to be with Eric. Emma doesn't suspect him of lying, especially when she uses magic on a mirror and sees proof of the real Ariel with Eric on Hangman's Island. ("The Jolly Roger")
After Second Curse[]
As Black Beard aids Prince Hans in capturing Anna and Kristoff and sentencing them to die by drowning at sea, he counts his own brush with death when a rival made him walk the plank, but he was saved by a certain mermaid. ("Fall")
After Third Curse[]
When Hook, Jasmine, and Aladdin end up on Hangman's Island while tracking Jafar, they wander into Ariel's hut and accidentally trigger one of her traps. Ariel later comes in and gives him a genie lamp which she believes is of Agrabahn origin. Realizing Jafar is in the lamp, Jasmine releases him from it, however, Jafar somehow breaks free of the genie curse and freezes all of them. After Jasmine uses magic dust to transform him into a staff and she frees Agrabah from a ring by sharing true love's kiss with Aladdin, Ariel asks to keep the ring since it's now just a normal trinket. Before donning her mermaid tail to swim into the Agrabah Gulf to get back home, she gives Hook a conch shell so he can communicate with Emma. ("A Wondrous Place")
In the Wish Realm, the mermaid Ariel befriends an old pirate named Hook, who becomes a drunkard after losing hope of reuniting with his daughter Alice. With Ariel's persuasion, Hook is able to pull himself out of it and resume his search for his daughter. ("Homecoming")
After Fifth Curse[]
Having come to the Wish Realm to rescue Jacinda and Lucy from this realm's version of Rumplestiltskin, Rogers leads Weaver to his old hovel by the seaside, where he recounts losing himself in drinking after losing his daughter, if not for a friend who helped bring him out of it. Using a conch shell, he summons this "friend", who promptly surfaces from beneath the waves, revealing herself to be Ariel. The mermaid cheerfully greets him, noting that it's been many years since she last saw him and that he looks slimmer. When Ariel spots Weaver, whom she mistakes for Rumplestiltskin, she becomes alarmed and attempts to throw her trident at him, but Weaver shrinks her weapon into the size of a fork. After Rogers explains that Weaver is actually helping him defeat Rumplestiltskin, he requests some squid ink from her. Ariel tosses him a clam of squid ink and cautions him to use it wisely as many lives are at stake. ("Homecoming")