In the episode, The Babysitters, Janet asks Chrissy and Jack to babysit for her friend because she has a date that night and can't. Jack and Chrissy agree and go to the person's house to babysit. Watch the scene where Jack and Chrissy are in the room after the phone rings and wakes the baby up. You can tell that the baby is just a doll! Chrissy moves her arm three times and the baby is in the same position as before,(it isn't moving) yet it is supposed to be crying and wiggling around. Also, in a later scene, Jack is holding the baby and it switches back and forth to being a real baby and then the doll. Strange.