Why does your dog flop on your feet when you pet him?

Answer 1

Lying down on your feet, or connecting physically with you in bed, are den behaviors, and also a way of showing you that they recognize you as the higher-ranking pack member.

Pretty much all of your dog's common behavior is the result of the genetics passed along to him from his domestic and wild canine predecessors. Wolves and wild dogs exhibit many of the same behaviors that our beloved pets exhibit, and almost all are related to two of their primary activities- hunting and sleeping (in a den environment). There are many others of course- mating, playing, establishing and maintaining pack social order, all are key components of pack behavior, but in the wild those animals are generally hunting, or, more often, sleeping. Most all other behaviors, even playing, are done to hone their hunting skills, or to test the state of the continuously evolving pack hierarchy.