Stuart Freeborn details his inspirations for the sculpt of Yoda, saying he modelled Yoda on himself and Albert Einstein.
Empire of Dreams: The Story of the Star Wars Trilogy, 20th-century Fox, 2004, 1:39-1:40
STUART FREEBORN: "George showed me a few original sketches and I thought, 'Well, that's interesting, but I want something in more depth,' you see? And so I looked in the mirror and I thought, 'Well, something perhaps a little bit amusing about my face.' So I modeled something of myself. Now I've got to make him look intelligent. I got this photograph of Einstein and put the Einstein wrinkles in all around. I did a lot of thinking about it because he's got to be full of sublte action and movements, especially in the face and the body. And I put it all in, what was necessary, and finally it all worked."