(simile) To smile broadly, especially in a self-satisfied way.

(US, simile) Having a feeling of uncertainty and misapprehension due to being in an unfamiliar situation.

Alternative form of put the cat among the pigeons

(idiomatic, humorous) Why is someone not saying anything?

A purported inferior has certain rights or prerogatives, even in the presence of a purported superior.

Alternative form of look what the cat's dragged in

(idiomatic) Used as an ironic acknowledgement of someone's arrival, especially to imply that they are unwelcome or disagreeable in some way.

(idiomatic, somewhat dated, Britain, Ireland, New England) A rebuke especially directed towards children for having referred to a woman as "she", instead of using her name or an appropriately respectful title.

Alternative form of a cat may look at a king

(informal) Very little space (available) (of a very small room).