A family of biped spatial four-link mechanisms with two revolute and two cylindric joints is proposed in this paper. Three main categories, including eight configurations are put forward. The primary feature of these mechanisms is that they are made up of four links that are connected end to end through two revolute and cylindric joints, and among the links, two of them are designed as feet. These novel configurations are revealed by different methods and ways: The basic configurations are enumerated by traditional mechanism synthesis method; the conventional configurations are obtained by repetitious trial; the unique configurations are accidentally achieved by inspiration or intuition. Each of them has its own characteristic and can be an alternative option for biped robot design. Compared with most of the existing biped mechanisms, these configurations are simpler in structure and thus easier to control. The singular configuration is cleverly used rather than avoided to perform the walking and turning. Their structure descriptions and walking simulations are accomplished. Afterwards, the kinematic and stability analyses are studied, the design considerations are discussed, and foot-workspace analyses are carried out. Finally, four prototypes are developed to preliminary verify the feasibility of these proposed concepts.