While a robot-gecko or a robotic water-strider simply mimic their biological namesakes, at Dr. Shigeo Hirose Robotics Lab / Tokyo Institute of Technology they came up with a robot that can switch from 4-legged walking to 4-wheeled roller-skating!
It's amazing and cool to watch the bot turn his feet into passive wheels and skate up a slope in the videos.
Dr. Shigeo Hirose pursues the roller-walker hybrid technology since the mid-90s, "because walking robot has high terrain adaptability on irregular ground but wheeled robot takes advantage of moving speed on smooth terrain. In the past, active wheels were often used for wheeled locomotion. However installation of active wheels restricted walking machine's ability very much. Because active wheels need actuators, brake mechanism and steering mechanism. This equipment is so heavy and bulky that it's not practical solution for walking robot which has many degrees of freedom. Proposed hybrid mobile robot named "Roller-Walker" is a vehicle with a special foot mechanism which changes between feet soles for the walking mode and passive wheels for the wheel."