Visible crew/equipment: When Professor Higgins is having Eliza practice saying the letter H by blowing into a tube to make the flame waver, the paper she's holding is actually Rex Harrison's lines. Once the paper starts to burn and the camera angle changes, you can read them and it's practically all of his lines for the whole scene.
Visible crew/equipment: After Eliza has left Henry Higgins, he goes back home, turns on the record of Eliza's voice and sits down to listen. Behind him on the floor to the right, there is a shadow with quite a bit of movement, as if someone was nearby. There is no one else in the room; and it can't be Eliza's, because she is still outside the room, and hasn't approached the doorway yet.