Puppies pee next to the pee pads for a simple reason: they haven't entirely grasped the concept of pee pads. Let's face it: puppies could care less about pee pads, they are just there for human convenience. Helping puppies understand the concept of human convenience is out of question, but at least we can help them make good choices with clear feedback.
Puppies attack your feet for a simple reason: feet are fun! In order to better understand this behavior, it's necessary to put oneself into a puppy's "feet" ehm... "shoes." When puppies leave the litter, they are left with no playmates to play with and feet feature some distinct characteristics that make them particularly appealing.
When puppies bite your legs, you feel their sharp, needle-like teeth and your instinctive reaction is to move away. "More entertainment!" thinks the puppy, as he latches on more in hopes of being dragged for the ride. Jokes aside, the puppy nipping stage may feel like a nightmare to dog owners who are in desperate need of solutions to curb the puppy's relentless biting.