Austrian physicist Erwin Schrödinger proposed this thought experiment to demonstrate the apparent conflict between what quantum theory. It predicts on the microscopic level and what we observe on the macroscopic level: A cat is shut in a box with a 'diabolical device' that kills it or not, depending on whether a radioactive substance emits a particle in a given time triggering the device. After that time that cat is alive or dead. Therefore, the cat is both alive and dead simultaneously - a superposition of states.
It's important to know that this was a thought experiment and that it was never really performed - at least by Schrodinger and his colleagues, Einstein, Podlosky and Rosen.
Whether or not the quantum question appeals to you, this little kitty puppet with his tongue hanging out, might just be the fun experiment you need for an evening!