What does "like herding cats" mean — and why is it funny?

informal, humorous

Meaning

Describes a task that is nearly impossible because the people or things involved refuse to cooperate or move together.

Where it comes from

Emerged in American English in the 1980s and was cemented by a memorable 1990s television advert that showed cowboys solemnly 'herding' cats across the plains.

Why it is funny

The humor is the doomed mental picture. Cats are famous for ignoring instructions, so imagining someone trying to drive a whole herd of them across a field captures pure, comic futility.

Used in a sentence

"Getting six toddlers to put their shoes on at the same time is like herding cats."