You need two baby dolls and some stoppable music. (Lullabies are nice if you add the rocking requirement).

This game is really Hot Potato played with two dolls. Passed separately around a circle while music is playing. You could add the requirement of rocking the baby a set number of times before passing it on. It is hillarious to watch as guests try to finish rocking as quickly as possible so they are not caught with the baby. I'm afraid they are sometimes not very soothing and gentle. When the music is stopped, the guests who are left holding the babies are out. This can become quite funny by the end when there are just a couple of contestants left juggling the two babies, hoping to get rid of both at the same time before the music is stopped.