A cat? That wants to be fed??

*gasp!* :3

I've heard this is a sign of saying your family with some cats...

I believe its a kittenish instinct. They butt the mother's breasts to stimulate the flow of milk. Domesticated cats retain a lot of immature behaviour they use with us to "communicate". In fact, it might well be that domestication is mostly just encouraging the animal to behave neotonously, that is as kittens or puppies. One intriguing idea that civilized man is just man domesticating himself, and our most creative behaviour is also just neotony.

From what I've heard, Madbadger is also right. While much of the body language comes from kitten-&-mom communication, the things like head-butts become more of a signal in older cats. I read that head-bumping the side-torso of a cat is supposed to be relatively altruistic affectionate (for a cat). Rubbing with the side of the muzzle is much more a possessive scent-marking. Which is convenient, because us humans scent-mark with our hands.

If they want to communicate with us, they have to adapt to our size and our 'deafness' to cats' body language (ear signals, etc.). It's hard for them to rub up against our head & torso to request a share of food for breakfast, so they make do by trying to rub against our legs while we attempt to walk to the refrigerator.

Uhm hm. Cat's talk alright. It's just as well they cant say "mime" or we might panic and wipe them out before we realized that was "mime" in a good sense.