You only slap your creature if he's been bad, or you want to teach him not to do something. However, if you want him to do something that he does, or he's been good/being good, you rub his belly.
You have to feed him when he's hungry, and the sleeping part he takes care of on his own.
He should get bigger after a while, but I dunno. Mine isn't that big right now, either.
I chose the tiger thing, what did you choose?