The 28-year-old actress was cast as Frozen's well-meaning ice queen earlier this month. The former Fringe star joins newcomer Elizabeth Lail as Princess Anna and Greek actor Scott Michael Foster as Kristoff.
Once Upon a Time's Elsa still struggles to control her icy powers, according to reports. Her love for her sister Anna keeps her magic in check, but she is aware of the damage another loss of control could cause.
In addition to the official photo, Haig has been spotted in character in several other pictures.
Once Upon a Time is in the process of casting Prince Hans, who swept Anna off her feet in Frozen. The character was revealed to be not what he seems later in the movie, and the television series describes him as "a well-bred prince with a serious chip on his shoulder." The fourth season premieres September 28 on ABC.