This is a cat with no brain (it's plenty disturbing, be warned) exhibiting three different gaits in response to a treadmill:
http://www.youtube.com/watch?v=wPiLLplofYw
From the info:
"This has lead researchers to the hypothesis that, when a quadruped walks/trots/gallops (or walks/runs in the case a biped), minimal control comes from the brain, and most of the control is computed morphologically through an implicit feedback structure in the bio-mechanical design. This phase transition phenomenon is still an active research area in the field of Passive Dynamic Locomotion."
