Elsa from "Frozen" emerges from a bottle and shows off her powers in this short clip from the very end of Season 3 of ABC's "Once Upon a Time." This episode just aired yesterday, May 11, 2014.
"Frozen" is a Hollywood phenomenon, but the creators of "Once Upon a Time" generally don't dip into the well of completely animated characters. Many of the other characters on the show may have appeared in animated feature films, but they originally came from somewhere else - a book, a fairy tale, a legend. This time, though, the people behind "Once Upon a Time" made an exception, as Elsa exists nowhere else. She was created solely for the purposes of the film (though she does bear some slight resemblance to "The Snow Queen" in the fairy tale of that name by Hans Christian Anderson).
No word yet on who will play Elsa next season. Idina Menzel voiced her in the film, but she's a busy woman on stage on Broadway, so they'd be lucky indeed to get her. And this Elsa is blonde, and Idina is a brunette, so it's a bit unlikely.