Cara called Amy something silly
Amy (in mock shock): “Daddy, did you hear what Cara just called me?”
Me: “Yes, I did. She can say that though, because she has a big bum!”
Cara (in mock shock): “My not big bum, my pest!” (Translation: “I’m not a big bum, I’m a pest!”)
Amy: “No Cara, you have a big bum!”
Me (in real shock): *jaw drop*
Amy made the distinction between being something and having something, in a very brief and passing conversation. I was so impressed with that!
Incidentally, the reason that Cara says “My” instead of “I” is because she hasn’t made the distinction between “Your” and “You’re” yet. She knows “Your” in the possessive sense, so when we say things like “You’re a big bum”, she’s responding to “Your” with “My”, as opposed to “You’re” and “I am”. I have tried (in vain) to explain the distinction, but I just get silly grins in return... so it’s either as I suggested here, or she’s just being downright cheeky.
Either possibility is as likely as the other! :o)