Zelena (Once Upon a Time)
In December 2013, Rebecca Mader was cast as the Wicked Witch of the West. She made multiple appearances during the second half of season three and was promoted to a series regular for the show's fifth season. The role of the Wicked Witch of the West was written specifically for Rebecca Mader. It was announced that the writers had chosen not to continue with Zelena's storyline and Mader would not be returning for the seventh season of the show. However, Mader later revealed that she would be returning for multiple season seven episodes.
Radek Zelenka
Zelenka was re-introduced in the mid-season-1 finale "The Storm", Martin Gero's second "Atlantis" episode. Gero had had difficulty with laying out the dangers of the storm and its solution in a quick and entertaining manner with just the McKay character, and Brad Wright was not opposed to introducing another expository character. Zelenka has since frequently appeared for expository scenes in the control room with McKay and the leader of the Atlantis expedition. Zelenka's given name is first mentioned by McKay in the season 1 finale "The Siege"; McKay had previously been unable to remember Zelenka's name. The producers chose "Radek", a fairly common Czech given name, without input from Nykl. When Colonel Samantha Carter (Amanda Tapping) replaced Dr. Elizabeth Weir (Torri Higginson) as the leader of the Atlantis expedition in season 4, the producers shifted the emphasis of Zelenka's collaboration with McKay to his interaction with Carter. By the end of the show's run, the interactions between Zelenka and McKay become more subtle to the point where they finish each other's sentences and need fewer words and expressions to get by.