Walking robots are normally complicated affairs, but this ingenious device by “lonesoulsurfer" is powered by just one continuous rotation servo. It doesn’t even use a microcontroller. Instead of complicated electronics, motion is handled mechanically.
The robot's linkage system is made from a pair of bent paper clips, which progressively move its four legs. The back legs rotate up and down, twisting the body side to side, while the front legs pull the little beast along. The legs themselves are bent out of pieces of coat hanger, and soldered on to pivots made out of banana jacks. These rotate on screws protruding from the walker’s body.
The project write-up outlines things in a bit more detail, including how to cut out 10mm x 10mm U-shaped aluminum channel for the body, and servo modifications for continuous rotation. No advanced tools are necessary, so as ‘surfer puts it, “If you have never built a walking robot before and want to jump in the deep end, then this is the perfect project to start with.” He does note that actually tuning the walking gait can be a challenge, which he outlines at the end of the tutorial.