wouldn't be seen dead

beat a dead horse

To persist or continue far beyond any purpose, interest or reason.

Brown bread

[Cockney slang]dead

butter wouldn't melt in someone's mouth

The identified person appears to be benign, mild-mannered, or calm (but with an integral suggestion that, to the contrary, they really are untrustworthy, disagreeable, or mean-spirited).

come back from the dead

To experience a resurgence after one's productive years are assumed to have ended.

dead 'n' buried

Contraction of dead and buried.

dead air

An unintended interruption in a broadcast during which nothing is transmitted: a silent period on radio or a silent period with no picture on television.

dead and buried

Of an issue, moot, passed, irrelevant, forgotten.

dead asleep

Sleeping in a deep sleep