In Berlin, a laundromat was raided because it was a front for a brothel. You know what tipped police off? Men doing laundry.

The joke hinges on a gender stereotype: that men are unlikely to do their own laundry. Leno frames a police raid on a purported laundromat-brothel front as being exposed not by evidence of sex work, but by the implausibility of male customers washing clothes. The punchline uses incongruity—an ordinary, mundane activity (laundry) becomes suspicious when performed by the “wrong” demographic—to satirize assumptions about domestic labor and masculinity. As with many monologue jokes, the humor also depends on a mock-news setup, borrowing the authority of a reported incident to deliver a quick social observation rather than a detailed commentary on policing or prostitution.