Knock knock. Who's there? Cow says. Cow says who?

This classic knock-knock joke relies on a clever bit of wordplay and a playful subversion of expectations. The "who's there?" prompt in these jokes usually sets up a name that will lead to another pun, but here, the "Cow says" setup takes a delightful detour into the world of animal sounds.

The humor hinges on the listener's natural inclination to complete the phrase "Cow says who?" as if "who" is part of a person's name, much like other knock-knock jokes. Instead, the punchline cleverly reminds us of what cows *actually* say: "moo!" It's a simple, innocent twist that plays on the phonetic similarity between "who" and "moo," turning a standard joke structure on its head by delivering a literal truth instead of another punny name.

Knock-knock jokes have been a staple of lighthearted humor for decades, often serving as one of the first joke formats children learn. This particular variation is a perfect example of how they can use familiar phrases and sounds to create a moment of unexpected, silly fun, making us chuckle at the straightforward answer disguised as a clever misdirection (Review).