Eight mini servo motors and an assortment of acrylic pieces combine to create the QuadBot, a low-cost, four-legged robotic pet you can assemble in under an hour. The kit doesn’t come with brains or batteries; add those yourself. Each leg uses two servos, making this a 2DOF (two degrees of freedom) walkerbot.
Exercising a bit of overkill, I tried out my QuadBot using a Dagu Spider controller, which can run up to 48 servos. For a less expensive option, try an Arduino Uno coupled with a servo shield.
QuadBot is tricky to program, but its designer, Russell Cameron, provides numerous examples on letsmakerobots.com under the username OddBot.
As with other walking robots, you should watch battery weight. Use small NiMH cells, not alkalines. I got 15 minutes of playtime with two 3×AAA packs wired in series on the underside of the robot.