Builds by Hiro Labo of Osaka Electro-Communication University's Department of Electro-Mechanical Engineering
For more details on how LEGO's pneumatic parts were used, see the following video:
Simplified Passive Walkers
Check out this passive walker, which utilizes a shaped foot. Tad McGeer's development of passive walking with knees is described here.
Notice how rubber feet were added to increase traction on inclines, or when pulling the robots.
Due to their small sizes the linkage dimensions of some of these walkers had to be modified somewhat to be built in LEGO, but they still walk fairly well.