Brady Bunch, The - Peek-a-boo
In the episode "Goodbye, Alice, Hello", Cindy and Bobby are in the garage talking about how they are mad at Alice. Alice is outside the garage and is hanging laundry or something. She overhears her name and sneaks over to hear what the kids are saying about her without being noticed. Here is where the slip-up occurs. Alice goes to the back of the garage where she can clearly be seen and the kids act like they can't see her.