A Japanese paper-modelling enthusiast has constructed a bipedal “robot” dubbed the “Paper Robot III” (or PR-III). Judging from the intricate nature of the design which is visible in the photos, the PR-III appears to be a labor of love, and has been painstakingly constructed almost entirely from paper, with the addition of a few wooden shafts serving to increase overall and drive the “engine” – a series of paper cogs and elastic bands which are wound up to set the PR-III walking.
Detailing the construction of the PR-III, its designer explains that it was difficult to get the balance right, though the desired poise was eventually achieved after several redesigns through trial and error. The PR-III's legs are powered forward by a crank attached to a two-stage gear which decelerates the speed of revolution that is initially gained from the wound-up elastic band mechanism to a more manageable rate.
If you'd like to build your own PR-III, it is available as a self-assembly kit for ￥3000 (roughly US$40), plus shipping. However, be aware that you'll be required to surmount the challenge of navigating a non-English website in order to arrange purchase and delivery.
The video below is an interesting look at how the PR-III was constructed.