There are three kids dolls as far as I know: the bear, the dino, and the unicorn. I just noticed something in the game today.
One, that they do have an increasing friend bar too, and two, their eyes change every now and then. I think that the increase in the friend bar changes the eyes of the doll somehow.
It's cute, but it's also at least informational. New levels of friendship with the doll unlocks more interactions that can trigger emotional states (inspired).
Just something I'd like to share because I found it interesting.