In the movies, Kenny Baker controlled the 2-legged R2 by putting his legs through hoses that connected the droid's torso to the feet. The intention was that we weren't supposed to notice them, they magically disappeared when 2-legged R2 went to 3-legged mode because they were using a remote-control R2 instead of a Kenny Baker-control R2. I think they CGI'ed out the hoses in TPM but Kenny was using them even then. Here are a few images from the films (the last one is TPM and you can't see the hoses too well, but you can see the cut-outs in the feet where they lead into):
It dawned on me that Hasbro has never done a figure of this version of R2-D2, and I wonder if there's anybody out there who would want to see it. It's a very authentic version of R2 obviously, but to realize it in 1:18 action figure scale would almost certainly make the legs immobile and R2 just doesn't have much going on with his legs unable to move - it's sorta all he has. But on the other hand, it'd be interesting to have a screen-accurate version of R2 like this, maybe they could have the hoses be removable to solve the movability issue.
So, does anybody out there actually want an R2-D2 like that?