EW: After a brutal hike up icy peaks to the Once Upon a Time set in Arendelle, we cornered the showrunners of ABC’s fantasy hit and demanded answers about season four’s much-buzzed-about Frozen storyline. Is Olaf going to be on the show? Are they going to give Elsa a love interest? How big a part of the show will Frozen be? And who is Elizabeth Mitchell playing, exactly? After a brief chase involving reindeers, sleighs and trolls, writer-producers Edward Kitsis and Adam Horowitz finally agreed to take our questions about their live-action take on the biggest animated movie of all time.