I love when actors make little mistakes! It makes the show more memorable, and like someone else mentioned, it's one of the joys and thrills of live theatre!
-When I saw Wicked for my 10th time...The actress playing Glinda (who will go un-named), missed a line when she was mentioning to Morrible & The Wizard about how to capture Elphaba. I didn't notice it, but some other fans and my mom did. She missed the whole line!
-On the Wicked Tour in 2006, during the middle of For Good, there was some really weird boom...about 30 seconds later, the mics went out and you couldn't hear Elphaba and Glinda singing. They kept singing, probably not even realizing something was wrong. They finished the song, started laughing, hugged, and then a stage-hand pulled the curtain they use for Elphie's melting all the way out, and they announced that there were some technical difficulties.
-On July 29th, 2006 Tina Maddigan kicked her shoe into the audience during Not That Kind Of Thing at The Wedding Singer! During a scene, the man who caught it sneaked up to the stage and dropped it in a shopping bag. Then when Richard came out, he mentioned about Tina only having one shoe on. She laughed about it and put the other one in the bag. It was a riot! And the audience laughed and clapped for a minute or so. At curtain calls, her applause was SO loud! It was great.
"Sing 'till you're breaking glass or you're breaking down"