Once Upon a Time: Possible casting for new "Frozen" characters

At the end of the last season of Once Upon a Time, we were teased about the coming of "Frozen" character Elsa. But as it seems now according to The Wrap, Elsa won't be the only one making an appearance her sister Anna and the goofy dude Kristoff will be making an appearance too. 

According to The Wrap, Once Upon a Time creators have casted Georgina Haig (Fringe) as Elsa, Scott Micheal Foster (Cappie from Greek) as Kristoff and newbie Elizabeth Lail as Anna.

Although it is unclear how Kristoff and Anna are going to enter the show, what is clear is how Elsa enter through the opening of the portal when Rumpelstiltskin killed Zelena. 

What i wonder about is if Olaf is going to be joining too. I would really like that.