Have you ever seen Cosmopolis? It's a 2012 movie directed by David Cronenberg, starring Robert Pattinson. It's about a billionaire riding around in a limo all day, trying to get a haircut. It's a fantastic movie -- weird, philosophical, raising questions it refuses to answer cleanly. Something I especially love about it, though, is the scene where the protagonist and one of his employees start joking around about an unnamed poem where the rat becomes a unit of currency.
It's a strange scene, one of the only ones where the protagonist appears to be having any fun whatsoever. The two men explore the concept as it would relate to the financial system: rat markets, pregnant rats, the prices of rats rising and falling. The poem itself is a mere curiosity, meant to deliver the concept which drives the exchange.
Out of curiosity, I looked up the poem after the movie ended, and it blew me away. It's "Report from a Besieged City," written by Zbigniew Herbert in 1982. The movie never mentions it by name, only casually references the one line, but I think it adds an incredible irony to the film and this scene in particular. I've copied a translation of the poem below the readmore, done by Czesław Miłosz.
Content warning: war and every horrible thing that comes with it