'Once Upon a Time': How about that surprising introduction?

The ABC fairy tale mash-up series “Once Upon a Time” surprised many viewers with its latest season finale, which aired on May 11.

Season finales of the show often tease what new fictional world will be introduced in the next season (past universes have included the “Peter Pan” world and that of L. Frank Baum’s novel “The Wizard of Oz”), and the end of the season three finale appeared to tease the introduction of Queen Elsa from Disney's animated film "Frozen."

While “Pan” and “Wizard” are more established fantasy worlds, “Frozen” is comparatively new, with the film (which was based on Hans Christian Andersen’s “The Snow Queen”) having just been released this past November.

Questions still remain: Will Elsa be the new villain for the next season? (The movie “Frozen” concluded with Elsa having harnessed her powers over snow and ice, at peace with her sister Anna, and presumably ruling over the kingdom of Arendelle). Will the princess Anna, or other “Frozen” characters like Anna’s love interest Kristoff, be introduced? And will actress Idina Menzel, who voiced Elsa in the film “Frozen,” play Elsa in “Once,” or will the role go to someone new?

Some critics seem split on whether introducing such a new character is a good idea. Washington Post writer Emily Yahr noted that “Once” “managed to steal the spotlight in a huge way” and called Elsa’s introduction “a truly brilliant piece of product placement-engineered plot” and “a genius move that will only benefit both franchises.” 

Meanwhile, Entertainment Weekly writer Hillary Busis found it “a bit weird to think of Disney's newest royal almost immediately joining the ranks of old, established properties like Snow White and Belle," asking, "Is her introduction coming too soon?," though Busis noted that "we can't really answer that until we see how the show ends up handling Elsa – not to mention who ends up being cast as her.”