Actors Tyler Jacob Moore and John Rhys-Davies will join the 'Once Upon a Time' cast as Prince Hans and Troll King Pabbie, both key characters in the Disney animated film 'Frozen'.

The casting update was released just days after a promo of the 'Frozen' based world in 'Once Upon a Time' Season 4 which was shown to the fans at the San Diego Comic-Con on Saturday.

Prince Hans' voice actor was Santino Fontana while Pabbie was voiced by Ciaran Hinds.

Moore is known for his portrayal of Tony Markovich in the Showtime series, 'Shameless'. Rhys-Davies is best known as Gimli in the 'Lord of the Rings' trilogy.

'Once Upon a Time' creator Adam Horowitz welcomed the actors via Twitter on Monday, "We're thrilled to welcome John Rhys-Davies to the #OnceUponATime family as the voice of everyone's favorite rock troll -- Pabbie! #ThisFall!" he posted, "Excited to welcome @tylerjacobmoore to #OnceUponaTime as #Frozen's Hans. Hope you come meet him this fall in Season 4!"

Tyler Jacob Moore also expressed his gratitude over Twitter on Monday, "I'm overwhelmed by you #OUAT and #Frozen fans! Thank you for the kind welcome. I'm honored to be apart of this passionate fan base/family!" Moore said.

Elsa is played by Georgina Haig, Anna by Elizabeth Lail, and Anna's love interest Kristoff by Scott Michelle Foster. Georgina wore Elsa's iconic blue gown to the 'Once Upon a Time' panel at the Comic-Con event.

The story of 'Frozen' was brought to the series in the Season 3 finale of the show.

Season 4 will explore Elsa's backstory via flashbacks. Viewers will be taken back to Arendelle to find out how Elsa fell a prisoner to Rumpelstiltskin.

Elsa could potentially be a villain in Storybrooke, according to Entertainment Weekly. It could have something to do with her inability to control her ice powers.

The fourth season of 'Once Upon A Time' is set to return on September 28.