The Wicked Witch of the West won't be the only "Wizard of Oz" character that will appear in the world of "Once Upon a Time." 

When the series returns, the ABC drama will introduce the Wicked Witch's (Rebecca Mader) polar opposite: Glinda, the good witch. Casting is currently underway for an actress in her mid to late twenties to play Glinda, who is described as warm, elegant, clever and kind. 

While Glinda is a strong character, she will not be in top shape when fans first see her. She will have been in isolation for years, which has made her lonely and cautious, yet unyieldingly optimistic. 

TVLine also reports that "Lost" alum Eric Lange will be joining the cast as a young Prince Leopold for a fairytale flashback. He will make his debut in an Enchanted Forest flashback in episode 18, which is called "Bleeding Through." Viewers will see that Leopold does not want an arranged marriage. Instead, he wants to fall in love with a woman who he can love and trust. Unlike many other kings, Prince Leopold is described as down-to-earth and humble.  

Eva Bourne will also appear in the episode to reprise her role as young Eva. 

Also, when the series resumes, Hook (Colin O'Donoghue) will have a tough time reconnecting with Emma (Jennifer Morrison), who has no recollection of the roguish pirate. 

"She will be very wary" of Hook, co-creator Edward Kitsis told TVLine. "I mean, if someone knocked on your door wearing leather and guyliner and tried to kiss you...? He's lucky he didn't get a baseball bat to the head!" 

Regina (Lana Parilla) will also meet someone from her past in episode two: her true love, Robin Hood (Sean Maguire). Kitsis said the two will "meet under interesting circumstances - heightened, intense circumstances - as one does on our show." 

Rose McGowan will also reprise the role of young Cora in Episode 18. 

McGowan first appeared as Cora in the March 2013 episode titled "The Miller's Daughter." In the episode, it was shown through a flashback that Cora and Rumple were once romantically involved. That is, until Cora removed her heart to pursue power as Prince Henry's wife. By episode end, she had given birth to baby Regina. 

Cora is expected to add to the show's complicated family tree, which will add two new branches by the end of the season. 

Additionally, co-creator Adam Horowitz said the fourth episode back, called "It's Not Easy Being Green,' will shed light on the Wicked Witch, as well as her issue with the Evil Queen. "She's got a whole backstory and mythology," Horowitz said. "We used the original [L. Frank Baum] book as a jumping-off point, and then spun her in a hopefully unique, Once Upon a Time way."

He added that when the Wicked Witch meets with the Evil Queen, "There are sparks that fly."

Meghan Ory, who played Ruby/Red Riding Hood/the Wolf in season one and two, may also return to the series. 

The next episode, "New York City Serenade," airs Sunday, March 9 at 8 p.m. on ABC.