It's now the second time this has happened, but I've been tinkering away at a little robot design only to find a similar one found by a fellow contributors.
This puppy has 2 legs and a set of castors on the front for stability with the initial design inspired by the amazing creations of Theo Jansen. The leg design is based on a six bar linkage which I best found explained at http://www.mechanicalspider.com/.
Getting the right link lengths was probably the trickiest part and I went through quite a few versions until I got just the right combination of step length and step height.
The stick on eyes and tail were my fiancée's idea and really give the little guy some personality.
I can't help but think of the line from the movie "Sleeper" :
"What does he do, leave little batteries around the house?"
I certainly would have struggled if I didn't find the mechanicalspider demo.