Is everybody ready for the "trio of terror?" 

The residents of Storybrooke will finally get rid of the ruthless Snow Queen in the midseason finale of "Once Upon A Time" season 4, and they will also formally say goodbye to their new friends Elsa and Anna as the sisters return to Arendelle.  The people of the mystical village might think that they can go back to living their lives, but little do they know what they're about to face — they have to be on guard once again as more evil forces are lurking right around the corner. 

This time, "101 Dalmatians'" Cruella De Vil, "The Little Mermaid's" Ursula, and "Sleeping Beauty's" Maleficent will join forces to wreak havoc in "Once Upon A Time" season 4 episode 12. Executive producers Edward Kitsis and Adam Horowitz shared this news via an exclusive interview posted on the Entertainment Weekly. 

"We've always said evil is not born, it's made. One of the things we're so excited about with these three villains is showing their origin stories. We've never seen the origin stories with Maleficent, Ursula, or Cruella, so we're excited about that," Kitsis teased. 

When asked how they chose the next characters that they will introduce in the series, the executive producer shared, "We always wanted to bring Maleficent back. We thought, 'What is the greatest team of evil we could gather to go up against?' Ursula we teased in the Ariel episode last year, and then Cruella, for a while, we just always wanted to bring her on the show and couldn't figure out how because in the movie, she was kind of [1950s]. You always want to put your twist on it. For us, Cruella just fit into this trio of terror." 

The plot allegedly revolves around the villains' quests to find their own version of "happy endings," although it could mean that they have to clash with Emma and the rest of the Storybrooke heroes along the way. 

The series executives also revealed that Cruella de Vil will be portrayed by Victoria Smurfit, Ursula will be played by Merri Dungey, and Maleficent will be portrayed by Kristin Bauer Van Straten. 

The midseason finale of "Once Upon A Time" season 4 will air on Sunday, Dec. 14, and it will return on March 1.