there was no real cat lol, it was just a 1935 thought experiment by Erwin Schrödinger to show how ridiculous quantum superposition would sound if you applied it to something normal, like a cat. he actually said later he regretted the example because everyone took it way too literally.
still gets used in physics classes all the time, and comes up a lot in debates about "many worlds" interpretation stuff too.
he actually said later he regretted the whole example because people took it way too literally, like they thought there was an actual cat that was both alive and dead. it was supposed to show how ABSURD that idea is, not endorse it.
it's also become a weirdly popular tattoo choice for physics nerds lol
my professor used to say if you think you understand the cat thing, you don't understand quantum mechanics yet lol
worth saying Schrodinger was actually critiquing the Copenhagen interpretation, not endorsing it, people forget he was the skeptic here
there's a real experiment called quantum Darwinism trying to explain why we never actually see superposition at macro scales, kind of related to this whole idea