겉똑똑이
surface-smart-person
A person smart on the surface.
Some site had this as "Penny wise, pound foolish." I suppose a person behaving that way is a superficially smart person. But I don't see the specific link to that English proverb – it really just seems to mean exactly what it says: a superficially smart person.
I'm worrying about if I should go to the dentist. But last week when I had time one morning I didn't think about it – I hate going to the dentist.