Billy Wilder on actors learning their lines

“As someone who directed scripts that I myself had cowritten, what I demanded from actors was very simple: learn your lines.

That reminds me. George Bernard Shaw was directing a production of his play Pygmalion, with a very well-known illustrious actor, Sir Something. The fellow came to rehearsal, a little bit drunk, and he began to invent a little. Shaw listened for a while and then yelled, Stop! For Christ’s sake, why the hell didn’t you learn the script?

Sir Something said, What on earth are you talking about? I know my lines.

Shaw screamed back at him, Yes, you know your lines, but you don’t know my lines.