We know cats are liquid, as they take the shape of their container. And cats love any kind of container: boxes, dishes, shelves, closets, bags, or whatever they can get into. A cat's definitinon of "container" is pretty flexible, ranging from mom's purse to a rain gutter. We might even call a cat a "container-seeking liquid."
Chris Poole has recorded video of his cats Cole and Marmalade ever since they were kittens. Here is a compilation that shows how they like to try on any kind of container to see if they fit. And if they fits, they sits! -via Tastefully Offensive