Wow, I forgot all about Athlete! It every bit as nimble as the LER, actually more so, it's freaking cool to watch.
It starts out on top of Altair, then spider walks off the lander and rolls over to where ever it needs to go. Somewhere on them internets there is a really cool time-lapse of it doing this (during one of the RATS competitions maybe?). I'll see if I can find it.
What I don't know is if it stays under the module permanently, if so, shouldn't the legs be mechanically locked in place somehow to prevent EVER shifting. Over my years of maintenance, I can guarantee you, that
anything mechanical can fail (often at any time and usually when you need it most) So says Demon Murphy...
edit---
hehehe
And another one, not so campy. And it answered my question earlier.