sleeping giant

gentle giant

A person or animal of a great size or strength, yet who is of a friendly nature and not aggressive or threatening.

let a sleeping dog lie

Alternative form of let sleeping dogs lie.

let sleeping dogs lie

To leave things as they are; especially, to avoid restarting or rekindling an old argument; to leave disagreements in the past.

one small step for man, one giant leap for mankind

(used imitatively) A cliché used to exaggerate an accomplishment or milestone.

sleeping at the switch

Alternative form of asleep at the switch.

sleeping policeman

A speed bump.