Millie is a minor character on Once Upon a Time. She is the young and innocent half-sister of Alice, whom she met after her second visit to Wonderland. As Alice attempts to move on from her past, she swore not to mention her "adventures" to Millie due to her impressionable nature. However, the memories prove too painful for Alice and she ends up telling Millie the truth. Alice is later given a choice and she leaves her new family to enter a mental health asylum.
Before the Curse
Millie meets her new sister. ("Who's Alice?")
Alice is sent back to her world and emerges from a hole in the ground at the same spot she did as a child. Having just lost her true love, she breaks down and begins to cry, however, she's found by a young girl named Millie. The girls parents arrive, searching for her, and Alice is shocked to discover that they both share a father. Alice and father reunite after many years and then he awkwardly introduces Alice to her new family. Once they return home, Edwin questions how long Alice will stay, to which she says forever, as there's nothing left for her in Wonderland. Concerned by this comment, Edwin asks Alice to not speak of Wonderland again for the sake of Millie. During a family dinner, Alice's new mother, Sarah, suggests that Alice meet a new man to begin her future, but the mention of this idea horrifies Alice, who refuses as she's still heartbroken. That night, during her sleep, Alice has nightmares about the death of Cyrus and she calls out for him. Millie hears this and asks her who he is, so Alice tells her the truth. However, Edwin and Sarah overhear this, frustrating them and they ask Alice not to mention it again. In the morning, Sarah introduces a young boy to Alice in hopes that they hit it off, however, Alice storms out, refusing to talk to him. Her father follows and she realizes that he doesn't believe her about Wonderland. Edwin gives his daughter a choice, marry the boy or go to an asylum. Alice chooses the asylum. She is later picked up by Dr. Lydgate in his carriage and they had to London. Alice refuses to let her father visit and then she leaves without saying goodbye. As the carriage drives off, she watches Edwin, Sarah and Millie together as a family, the family Alice never had herself. ("Who's Alice?")
After the Curse
Millie makes a new friend. ("And They Lived...")
After spending time locked away in the asylum, Alice is broken out by Will Scarlet and the White Rabbit, two friends she made in Wonderland. They bring her back, via portal, to the magical land where she is now up against the Red Queen and Jafar whilst on a quest to save her true love Cyrus. Alice and Cyrus are soon reunited, and later on, with the help of others, are able to work together and ultimately defeat Jafar once and for all, as he is turned into a genie and becomes trapped in a bottle for the rest of his days after trying to steal water from the guardian of the Well of Wonders, Nyx. The White Rabbit is then able to take Alice home, back to Victorian England, where she marries Cyrus. Among the attendants are Millie, who plays padda-a-cake with her new friend, Tweedledum. Alice is then walked down the aisle by her father, Edwin, and Millie watches along with Sarah, Edwin, and Alice's new friends from Wonderland as the White Rabbit joins Alice and Cyrus in holy matrimony. Following the ceremony, everyone from Wonderland says their farewells to Alice before heading home, via the White Rabbit's portal. ("And They Lived...")
Gallery of photographic stills released to promote the character.