Schrödinger's cat has to be the worst one.

In popular culture, it seems like people think Schrödinger's cat was some sort of crazy experiment where a cat was simultaneously alive and dead until the box was opened, all explained by the craziness of quantum mechanics.

In actual fact it wasn't a real experiment, it was a thought experiment used to highlight the absurdity of quantum mechanical superposition. I've had people (non scientists) say to me how stupid physicists must be because Schrödinger's cat is obviously impossible in reality, not understanding that the impossibility of it is precisely the point of the thought experiment.