The shirt that Dr. Cox's son (from Scrubs) was wearing made him look like Claus. They both have red hair! (though it may be hard to tell from this pic, but trust me, they do)

Done with watercolor pencils. I realized much too late that brown was the wrong color to use for the background because the Mad Duck blends right in (I chose brown because of the colors of Brick Road's first dungeon). There's no "undo" button when you're holding a paintbrush, though, so oh well. Live and learn.