Cats pretending to be kittens sucking - that's a rather different thing, and definitely less comfortable than being patted with a paw! They "knead" with their paws - which from a kitten is quite soft and stimulates milk flow. However, as they get older their claws grow bigger. My cat, in between biting my hand, also kneads my knee when he's being stroked - only it's modified into an excruciating form of 10-needle acupuncture. What's dafter still is when he "kneads" his paws in mid-air - lies on his back and stretches one paw, then the other.