Random Audience Member Picked by Kristin Chenoweth Stuns Hollywood Bowl with Voice

At Saturday night's concert at the Hollywood Bowl, Kristin Chenoweth chose a random audience member to join her on stage for a performance of "For Good" from Wicked.
The audience member (also, a voice teacher) Sarah Horn, explains:

Toward the end of the second half of the performance, Kristin wanders on to the pasarel. She held a mic up to a lady in front of me and asked if she knew the song "For Good." Nope. I took the chance, as I was directly behind Kristin, to stand up and wave and say, "I know the song!"

This is not like me - to jump up and wave my arms like a crazy person and raise my voice at a celebrity. As soon as she turned to look at me, I say right back down... and calmly said, "Hiiiii." ...

After this, she moved down the line and asked a guy if he knew the song and bantered with him for a few seconds. Afterwards, she said something about going back to pick me because I was a girl. Then, she invited me up on stage.

I sat there for a moment, stunned. Then the backup singer motioned for me to get up. I shot up out of my chair as my heart leaped up past my throat and started beating in my ears. I don't really remember what happened between the box and when I first set foot onstage except that there was now a microphone in my hand.

Kristin had no idea what was to come. And that's pretty much where the video picks up.