baby's chew toy: what ever delicate item you are currently working on (like eating the hair brush while you are trying to brush your hair. Then when I took the hair brush away, she chewed on my hair). Or the papers that I have so carefully organized on my desk..... and when all else fails- your fingers.
baby's favorite chew toy: the one of the many you spent money on, and then lost. So the child refers back to the first definition of chew toy.