. >> reporter: the story got the attention of legendary composer steven schwartz.ur babies, but do you have a favorite number? >> i do, but i'm not going to say what it is. ♪ popular, you're gonna be popular ♪ >> reporter: but schwartz did like this song, "popular," and he knew he wanted actress kristin chenoweth to sing it. >> steven schwartz says, i've got this song. just come for the meeting. it is with you in mind. i can't hear anybody else. i walked in and sang "pob popu"popular" for the first time, and i'm, like, i'm in. >> reporter: chenoweth went on to become the good witch, glinda. and the title role of the wicked witch went to broadway veteran idina menzel, who says at first she was a bit shaky. >> i was afraid i was going to get fired. they were rewriting things all of the time, and i wasn't good at cold readings. i was like a mad little student and ripping out pages, and kristin was so beautiful and her first take on everything was so funny and so right. and i was just the opposite. i just felt like a big mess. ♪ because of the wizard and me ♪ >> report