There are actually 4 hour put-ins for each new child that joins the show (as they obviously age out rapidly). I can only think of 2 other incidents that are close. Beauty and the Beast had a very young Chip, though not an infant, and he was occasionally replaced by a doll. Also, iirc, Titanic did have a very young child who was occasionally replaced by a doll.
The short-lived The People in the Picture had a 4 or 5 year old girl, who oddly did not seem to have an understudy.