Nickname for Dr Elliot Read (Sarah Chalke) in 'Scrubs', meaning she is hot but a bit of an airhead and clumsy as anything.
Elliot: Oh, Dr. Cox, does this lipstick make me look like a clown?
Dr. Cox: No, Barbie, no... it makes you look like a prostitute who caters exclusively *to* clowns.
Elliot: I'm sorry, that was my mistake, I keep forgetting that you're a horrible, horrible person.
Dr. Cox: Ooh, Backbone Barbie.