Fist of all, I have to show you the visual development - and some psychological attitudes - of these persons based on Cervantes' book.
Here, I've drawn Don Quijote thinking in a thin middle-aged man. To tell you the truth, I really wanted e silhouette which looked like a Chuck Jones's Willie Coyote, only because Chuck's drawinhgs are so charming. So, I made many studies in my sketch book for the Mancha's warrior. And stopped when I could watch a satisfatory result to it.
With the Don made, I could think in Sancho Panza. Thinking for contrast, because in animation, the character's visual is better watched for the audience when we made the opposite visual, and attitudes. Of course, Sancho came out easier than Quijote. I don't know why...
That's are the two previous result for these characters, that I liked so much.