Because he needed the money, Orson Welles signed to appear in a play where the rest of the cast was, to put it politely, inexperienced. He was the only real pro involved so on the first day of rehearsal, he made a little speech to the other players…
He said, "We're going to be doing this play for several weeks and the law of averages dictates that at some point, some egregious mistake will be made. Someone will miss a cue, someone will forget a line, something will happen. When this occurs, do not panic. I am on stage for almost the entire play and I have decades of acting experience. Every disaster that can possibly happen has happened to me and I can handle anything…
"So when something goes wrong," he continued, "do not attempt to ad-lib. Just leave it to me. Whatever it is, I will find a way to cover the error and continue on." The members of the novice cast were reassured by this and felt confident they were in good hands.
Things went well until opening night. In the middle of Act Two, the prop man accidentally rang a telephone in the wrong scene. There was no phone call in that scene and all the actors on stage froze, wondering what to do. Fortunately, Mr. Welles announced, "I'll get it," and they all relaxed, confident Orson would handle it. They knew he would answer the phone, ad-lib some sort of conversation and then work his way back to the text of the play.
Welles picked up the phone, said hello and pretended to listen for a second. Then he turned to the actress next to him, held out the receiver and said, "It's for you."