Here is some of the concept art I made when creating the Doctor. I ended up making quite a few sketches of him, just trying to figure out how his lizard-like limbs would work. You see, lizard limbs can attach themselves and bend at very odd angles ... most of which didn't look very pleasant on him... I ran into a similar problem with his little lizard fingers and nails.
As you can see, I also tested out some different eyes and effects - such as completely round eyes with spectacles and a long, thin mustache.
It took a good bit of time and effort, but I am quite happy with the results.
This clever guy first appeared at the very beginning of the Stupiders,
in issue 1, page 1.