In this paper we will present two humanoid platforms (Acroban and Poppy) developed in our lab to study biped locomotion and physical interaction. We will present how their morphologies (compliance, vertebral column, and soft ma- terials) produce human-like movements and natural responses to external perturbations. We will illustrate this behavior with the example of the socially guided biped locomotion. We will also discuss the very positive emotional reactions aroused when presenting Acroban to the general public. We will hypothesize that this behavior could be explained by the contrast between its crude visual appearance and its smooth and compliant movements which increases the impression of like-likeliness.