Английский словарь американских идиом - eager beaver

{n. phr.}, {slang} A person who is always eager to work or do anything extra, perhaps to win the favor of his leader or boss. * /Jack likes his teacher and works hard for her, but his classmates call him an eager beaver./ * /The man who was promoted to be manager was an eager beaver who got to work early and left late and was always offering to do extra work./