The dirt texture is actually a pretty simple effect- It's actually just a photo I took of some gravel that's been put on a layer set to 'overlay'. Trying to use hydraulics for the legs would be too bulky and fragile, so if I had to guess I'd say they're probably moved by muscle-like bundles of an electroactive polymer of some sort.
No that's actually just Photoshop 7. There's just a dirt texture put on between a layer of relatively flat color and most of the brushwork. It has some potential, but I'm not totally happy with the effect as executed.