"I not a baby"

So I like to refer to my boys as my babies.  Anytime I call Luke my baby he responds with "I not a baby."  This happens everytime.  The other day I called Luke my pumpkin and he said, "I not a pumpkin."  He is so cute everytime it happens.  I just put him to bed (for like the 20th time tonight) and said "goodnight baby."  To which he responds, "I not a baby."  If you ask him what he is he says, "I Lukie."