A cast member from 'Once Upon a Time' may have given away spoilers suggesting that Queen Elsa from the popular blockbuster "Frozen" may come back as a villainess in Season 4. Meanwhile, 'One Upon a Time' is scheduled to premiere in September this year.

This speculation was fueled by the very last scene of the Season Three Finale, where a character resembling Elsa was teased. The character in question magically appears from a puddle of blue liquid, and leaves a path of ice wherever she walks -- just like Elsa from the Disney hit-film. ABC Studios have yet to confirm whether this character is indeed Elsa.

Rumors though still persist especially after cast member Lana Parilla, who stars as Regina, confessed to E! Online that she did not know who was going to play Elsa. Is this an admission that Elsa is coming onboard for Season 4? At this point in time it is hard to say, even though TV/film crossovers form key elements in the 'Once Upon a Time' story arcs.

Apparently, even the stars were just as surprised that 'Elsa' appeared in the Season 3 Finale. Jennifer Morrison, who plays Emma, made it clear in the same E! Online interview that she herself was unaware of plans to bring 'Frozen' into the show.

"I think that it was a big deal that they were even approved to use Frozen on the show," Morrison added. "I have no idea what they are going to do with them."

Still, it is only logical for the Disney-owned ABC Studios to capitalize on the 'Frozen' hype. Although 'Once Upon a Time' does command a loyal following, ratings in past months have shown that viewership is dipping. Not to mention, ABC has already invested a substantial investment in production value for the show. Perhaps, a 'Frozen' crossover will breathe new energy into the show when it comes back to the ABC network this coming fall.

'Once Upon a Time' will continue airing in the same 8 pm time timeslot on Sundays, though the actual premiere date remains a mystery.