“Four is an interesting number because it is a shape that would arouse the curiosity of a cat. Most numbers are either open or closed. Number 8, for instance, is closed; a cat has no business to look inside. A cat likes to peer into something that is half open—a little bit open—a mystery. Number 3 is obvious; number 1 is nothing; 5 perhaps is more intriguing, but 4 certainly is perfectly designed and engineered for a cat to look inside and find out what is going on.”