Personality Idioms

source: ReadySteadyEnglish
--an eager beaver (try too hard to impress people and work too much)
--be as hard as nails (don't care much about other people's feelings)
--a cold fish (quite distant and not very friendly)
--a fat cat (makes people dislike the way he/she uses money or power)
--having a heart of gold (very kind and generous)
--a mouse-potato (a person who spends too much time on the computer)
--a pain in the neck (a person who is difficult and unpleasant)
--smarty-pants (you think you always know best)