"Baby Book"

Hayden refuses to call Landry "Landry". He always refers to Landry as "Baby." We have tried to get him to say her name numerous times and he always goes back to plain old "Baby." Funny thing is that she answers to it. Anyway, tonight Landry was about to get into something and I said, "Landry Brooke!" Hayden quickly echoed, "Baby Book!" I guess that we have graduated to something beyond just "Baby."