sweet young thing

be a thing

To exist, or to be available, widespread, possible, or a common practice.

best thing since sliced bread

Alternative form of greatest thing since sliced bread.

best thing since sliced pan

Alternative form of greatest thing since sliced bread.

bright young thing

One who is youthful, clever, eager, and high-spirited in manner and attractive in appearance.

chance'd be a fine thing

Synonym of no chance or fat chance, with a somewhat more cheerful attitude.

do one's own thing

To do what one considers to be best suited or most satisfying for oneself; to do what expresses one's distinctive interests or talents; to do as one chooses.

do the decent thing

To take the most honorable or appropriate course of action, even if is not necessarily in the person's own interests.

do the right thing

To do what is ethical or just.