In season 2 episode 6: Take Two Aspirins when Mrs. Kravitz goes up to Samantha & Darrin's room to get her soup dish back she notices the door for a room they are supposedly making for the baby. She opens the door, shakes her head and closes the door. As she is walking away she hears a knock, stops in her tracks, hears the knock again and puts her ear against the door and once again hears the knock and that's when she runs away screaming but you can clearly see that her mouth isn't moving or even open at all.