canary fit

canary in a coal mine

Something whose sensitivity to adverse conditions makes it a useful early indicator of such conditions; something which warns of the coming of a greater danger or trouble by a deterioration in its health or welfare.

cat that ate the canary

A person who appears self-satisfied or smug, especially while concealing something mischievous, prohibited, or private.

fit for a king

Lavish; luxurious.

fit out

To provide a thing, a group, a person or oneself with requisites; to kit out.

fit the bill

To satisfy a need; to serve a purpose; to fulfill specified requirements.

fit to be tied

Very agitated or distressed; also, very angry; enraged, furious.

fit to wake the dead

At a very high volume; extremely loudly.

have a fit

To experience an epileptic seizure.